william-james proposed four marks: ineffability, noetic quality (it feels like knowledge, not mere feeling), transiency, and passivity. Later researchers added unity, sacredness, and positive mood.
What every tradition warns is that the experience is not the point. An experience passes; what matters is what it permits to become stable. “You are not enlightened,” said one teacher, “because you once had a realization. You are enlightened if you live from it on Tuesday afternoon.”