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Guru in Sanskrit or Garu in Pali, means teacher.
But in the context of your question, Guru is a spiritual teacher who confers blessings on his disciple, and whose disciple has devotion towards the spiritual teacher. The disciple trusts that the spiritual teacher will lead him to liberation. The disciple treats the Guru as a Buddha or a deity. The Guru has a direct spiritual link or spiritual connection with the disciple. The Guru is also called the Vajra Guru. The Guru may perform ritual empowerment or initiation upon the disciple. This is found only in Tibetan Buddhism/ Vajrayana.
Ganesha as a deity and Guru, is also found only in Tibetan Buddhism/ Vajrayana, not as the Hindu God, but rather as an emanation of Avalokiteshvara.
In Theravada Buddhism, the only true spiritual teacher is the Buddha, to whom all take refuge in. Refuge in the Dhamma (teachings of the Buddha) and the collective Sangha is also taken, but not refuge in any individual teacher. The ordinary teacher, say venerables like Ajahn Brahm or Ajahn Yuttadhammo, do not have spiritual or supernatural links to their students. What the students have, is admirable friendship (kalyanamittata) with their ordinary teacher, based on SN 45.2 and AN 8.54. The student does not have devotion towards their ordinary teacher but they may have trust in him. The ordinary teacher does not confer supernatural blessings upon the student. The student does not value the words of the ordinary teacher as being equal to the words of the Buddha.
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Guru is a word (Hindi and Sanskrit) that literally means teacher. Connotatively it comes to mean master, spiritual guide, etc. Rinpoche is Tibetan for Guru (amongst one meanings). All gods and goddesses can be guru [M.] (gurudain [F.]). Jupiter is also considered as a Guru. Ganesh is also a guru.
Guru-shishya (teacher-disciple) relation is very specific to Ancient Indian subcontinent, where oral transmission has been a form of teaching (at times the only). Within Tibetan Buddhism, this teacher-student relation is very important as the answer by @Zac Anger emphasizes.
In contemporary India, people still call their spiritual teachers as guru.
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Short answer: no, not really, but if you want more confirmation you should find a local respected teacher from a Tibetan, Nepalese, or Mongolian lineage and consult with them. Most likely your best bet would be to find a living guru.
Long answer: I'm mostly familiar with Chan (Mahayana) and Theravada. In the Theravada the idea of a guru is almost nonexistent, and in Mahayana (including Chan/Zen), a specific master is important but not held at the same level that a guru is in Tibetan Buddhism/Vajrayana. Gurus are essential in the Vajrayana because some of the teachings are esoteric, not to be carelessly revealed to anyone because they require guidance and preparation. Usually "guru" in Buddhism refers to your immediate teacher, but can also refer to anyone in their direct lineage (your teacher's teacher, their teacher, etc., back to Padmasambhava, Virupa, Tsongkhapa, etc., and further back to the historical Buddha, Vairocana, or some other Buddha. In casual usage, this is less common and guru usually means your primary teacher, the one you're loyal to and show devotion towards in this lifetime, in person.
Could Ganesha be your guru? Well, Buddhists don't exactly believe in Ganesha in the same way that Hindus do. Vajrayana has Vinayaka and sometimes Heramba, who is essentially Ganesha, who is a deva (or demon, in at least one form), but deity yoga (in Vajrayana) is different from Guru yoga, and outside of Vajrayana as far as I know it doesn't exist at all (though we do revere other Buddhas and Bodhisattvas, which are a similar concept but not exactly the same).