I used to think it as "Flow." I now think of it as "The Timeless Now of the Divine Spirit." Losing yourself in the moment. Being so aware, so alive, so in the moment, that the self disappears, and the "what you are doing in the moment" is everything.
Time falls away. The rest of the world disappears.
I could sometimes get to that state by long-distance running, sometimes by deep meditation. I could often get there acting in a play or performance piece, and lately, rarely, (usually in rehearsal), I can get there playing music.
It's funny. Many years of performing, many years of losing myself in the flow. That is the kick. That is the secret. That is the glory. Better than accolades, better than awards, better than applause, better than money or fame.
Losing yourself in the moment...