What is "spirit" in Holy Spirit?

St.Kolbe has a direct answer to your question.

St.Kolbe uses the distinction, teaching, the Uncreated Immaculate Conception as the Holy Spirit, the third person of the Holy Trinity. And the "Created Immaculate Conception" pertaining to the "Spirit" that resides, in Mary, when She introduced Herself newly, to answer, St.Bernadette question, "Who are you?"

When St.Bernadette asked, "Who are you?"

Mary introduce Herself not simply as the Mother of Jesus Christ, that St.Bernatte could easily relate to, but She answered, "I Am the Immaculate Conception". St.Kolbe, was puzzled, as if, Mary was possessed, by a "Divine Spirit".

And so, if one could contemplate, what St.Kolbe had seen, seeing, that there is a "Uncreated Immaculate Conception" and "Created Immaculate Conception". This two are Spirit, the as other as, being "supreme" being co-substantial with the Holy Trinity, and the other "spirit" proceeds proceeds from the Father and the Son, that was "qanah or birthed" by the Holy Spirit the Uncreated Immaculate Conception, as the spirit that dwells in Mary perfectly, completely and mystically, saying, "I Am the Immaculate Conception", a divine person, that possessed Mary's whole being, and St.Kolbe coined this phenomenon, "quasi-incarnation".

In scriptures, the closest description of "Created Immaculate Conception" being a "spirit" or "divine person", is written in the mysterious wordings of Proverbs:22. There is a Spirit that gave birth to a spirit.

The LORD possessed me in the beginning of his way, before his works of old.

https://biblehub.com/commentaries/proverbs/8-22.htm

And this "spirit" dwell and rested in Mary's heart, that was hewn by Seven Sorrows or Seven Pillars.

Wisdom hath builded her house; She hath hewn out her seven pillars:

Then the creator of all things commanded, and said to me: and he that made me, rested in my tabernacle,-Sirach24:12

And, the play of words, is hard to grasp, if one, doesn't see that the word "tabernacle" refers to the heart of Mary, the Seat of Wisdom.

And to add another important verse, with regard to wisdom pertaining to a spirit that was qanah or birthed in reference to Proverbs8:22.

For wisdom is more active than all active things; and reacheth everywhere, by reason of her purity. 25For she is a vapour of the power of God, and a certain pure emmanation of the glory of the Almighty God: and therefore no defiled thing cometh into her. 26For she is the brightness of eternal light, and the unspotted mirror of God's majesty, and the image of his goodness.-Wisdom7:24-26

And finally to connect this view, to Catholic teachings, the Catechism teaches that the Abba Father had prepared a place to dwell for His Begotten Son and for the Holy Spirit in Mary, the tabernacle of God.

"Post it later, i will look for the CCC teachings.)

Normally I do not even attempt to answer if there Catholic are LDS questions since I know so very little about either, however the problem of understanding that God is a spirit and accurately what it is. Seems to plague all the denominations.

Therefore; I have decided that I will undertake to try to help clarify the concept and characteristics of the spirit. As you so accurately stated God is. And in order to worship. We must worship him in spirit. But actually what is a spirit?

When God created man he created he him in the likeness of God himself. So what does it mean in to be created in the likeness of God himself?

So let's look at Genesis and see if we can determine what is meant by in the likeness of God.

All Scripture is quoted from the new King James translation

Genesis 1:26 through 28 Then God said, "Let Us make man in Our image, according to Our likeness; let them have dominion over the fish of the sea, over the birds of the air, and over the cattle, over all the earth and over every creeping thing that creeps on the earth." 27 So God created man in His own image; *in the image of God He created him; male and female He created them. 28 Then God blessed them, and God said to them, "Be fruitful and multiply; fill the earth and subdue it; have dominion over the fish of the sea, over the birds of the air, and over every living thing that moves on the earth."*

And most importantly!

Genesis 2:7 And the LORD God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living being.

The Scriptures I have highlighted I highlighted in order that we may understand better the likeness of God himself. So taking them in the order that I have highlighted; let me elaborate on the meaning of each part.

1. let them have dominion over the fish of the sea, over the birds of the air, and over the cattle, over all the earth and over every creeping thing that creeps on the earth."

This characteristic is important to the image of God's, in that just as God has dominion over his creation, he has now given man the dominion over the other living and breathing portions of his creation.

2. *in the image of God He created him; male and female He created them. *

So God created man in his own image, and that certainly does not mean his the physical image. Since man and woman are very physically different, and that does not even take into account the difference between and a child and an elderly person.

3. "Be fruitful and multiply; fill the earth and subdue it; have dominion over the fish of the sea, over the birds of the air, and over every living thing that moves on the earth."

And this may be the most miraculous part of God's image; in that he has now given man not only the ability to create eternal life, but he has also given him the responsibility for creating life in order to continue man's dominion over the animals. And even more amazingly that life which God gave man the ability to create is life eternal.

In order for man to be able to pass on to his posterity eternal life he himself must have eternal life to pass on.

Genesis 2:7 And the LORD God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living being.

In accordance with this Scripture God breathed from his own self, the breath of life. Since we are talking about being in the image of God, God is eternal and being eternal soul also must his breath be eternal. And the next part says that man became a living being. (Other translations say man became a living soul.)

So what does becoming a living being actually mean?

Without going into a lot of detail what that actually means is that man has three parts; a body, a spirit, and a soul.

There is one very great differences between man and God, in that God is discarnate (stripped of flesh). The most difficult problem that man has with understanding God, is that very point. When God created man he tied his spirit to a physical body, but God exists outside of the physical realm. The best way I can think of and to illustrate this is that God is like the air surrounding the Earth.

God has no definite shape just as the air does not. God is on a restrained just as the air is not. Just as the air is everywhere, so is God everywhere.

Perhaps this excerpt; which I copied from a website, but cannot tell you now which one it was, will help you to understand.

In a general sense, discarnate spirits are able to travel throughout the universe, and they do so by use of their will, or thought. they can travel at the speed of thought, or they may choose to do so at a speed in which they are aware of the space they are traversing. Matter does not obstruct the spirits' movement. They are able to pass through air, earth, water, fire, any man-made material, etc.

Man is constrained by the physical world. However; God is not because God created the material world, and so the dimension in which God exists is not the physical or material realm.

All of that was said so that you might understand what the spirit is; however your question refers specifically to the holy spirit, and that takes us to completely different elevation. In order to talk about the Holy Spirit we must first understand the Trinity. While I understand that not all denominations, subscribe to the concept of the Trinity, we must understand the concept in order to distinguish the Holy Spirit.

When we speak of the Trinity what we are actually referring to is the Godhead. The Godhead is that which existed with no beginning and no end. Or in other words the Godhead is the only thing which existed. There was absolutely nothing else; no such thing as space, no such thing as time, no such thing as any material object. This is even before the creation of the Angels or heaven itself. The Godhead is uniquely powerful, by that I mean that the Godhead has abilities beyond any other part of the spiritual realm. The Godhead has the unique ability to create other spirits. With this unique capacity he created all other things, not only the material realm but also other objects in the spiritual realm, such as heaven and the Angels. One of the hardest things to wrap our minds around is the spiritual realm, and all of the things which we consider to be real actually exist in the spiritual realm; including the physical realm or those things which we can see touch smell or in other words those things which activate our five senses.

The human mind is not even capable of distinguishing between the temporal and the eternal. The material world is entirely temporal and that it must eventually pass away. The soul of man, the Angels, and the kingdom of God are eternal. Since man is unable to distinguish between the temporal and eternal how would he ever understand the Godhead which is infinite? What is meant by God being infinite is that God has no beginning and no end, this is the concept which man does not understand even though he may believe that he does.

The concept of the Trinity is the that the Godhead consist of three individual, and co-equal entities existing as one infinite being. Those three co–equal entities; we call for lack of better terms, the father, the son, and the holy spirit.

In each of these entities have, for lack of a better word, differing functions as part of the holy Trinity.

Since your question was directly concerning the Holy Spirit, the following website should be of interest to you. It has a much better explanation of the characteristics of the Holy Spirit than I can put into words.

http://blogs.blueletterbible.org/blb/2013/02/25/characteristics-of-the-holy-spirit/