Oomf stands for "one of my followers" on twitter.

It’s an acronym standing for Can’t Remember A Fucking Thing. It’s usually used to describe embarrassment at being unable to remember someone (CRAFT moment); going onstage as the lead in the latest theatrical performance and your mind goes completely blank (CRAFT situation); the next morning after a night when you got pissed as a fart and woke up in bed cuddling a traffic cone and a string of fairy lights wound round your prick.

your crush maybe, someone anonymous you don't want to mention their name

One of my friends
or, as on Twitter: one of my followers

twitter slang meaning, “one of my followers” often used negatively to talk about people behind their backs.

an onomatopoeia used to describe a person of extreme attractiveness

one obnoxious mother f*****