I think ESTA counts as a permit. I doubt you will be able to establish otherwise with any degree of certainty.
In that light, you should certainly disclose the denial. In other words, err on the side of caution. I suspect that Canada will not be terribly concerned about the reason for your denial, but if you answer “no” and they find out about your denied ESTA — which they probably will — then you risk a serious loss to your credibility and possibly serious difficulty with future visa applications.
Credit:stackoverflow.com‘