FSI

Forsure InshAllah (FSI)

This word is used when a flakey dude cant own up to make a real commitment and knows he's probably gonna flake. So he adds an "InshAllah" to the end of forsure.

Dude 1: Dude im totally coming tomorrow don't worry I wont flake.
Dude 2: Dude thats what you said last time
Dude 1: Nah dude this time FSI

*Tomorrow comes

Dude 2: Dude you totally flaked
Dude 1: Sorry dude, I was busy