"Oof" is an expression when you become surprised, alarmed,
shocked etc... And are about to yell "Oh Fuck" but realize there are seniors around or when u become
lazy to finish the exclaim "Oh Fuck" you stop halfway and say "Oof" or "OOOFFFfff" in
regret or lost hope.
Kaiz : Dude did u bring the
exam paper for corrections? Because teachers
gonna kill you if u aint got it.
Me: OOOOFFFF