Definition 1 of 1
(Note, there might actually be a reason involved -- but ainvayi is like a filler word, sort of like "whatever"... If fobbed off with that answer, it may be worth investigating further.)
The term has been made famous by its use in a peppy Yash Raj Films song.
2. Sunita to her friend Radhika: Why did you break off with Sunil, man? He was so nice!
Radhika: Ainvayi, dude.
Sunita: Arre? Just? You think hot guys grow on trees or what? Who's going to marry you if you continue in this manner?
Radhika: No, yaar, all the time he was touching me like anything, so tharki. It was like dating some naughty Indian uncle, thatandoldontask! By God, it was too much!
3. Nikita: Why did the Surd cross the road with some makkhan in hand? To get to the butter chicken on the other side! (laughs uproariously at her own PJ)
Ritika: Oh, God, ainvayi you are maaroing Bak-Bak!