The Brief: On social media NOOMF is an acronym for "not one of my followers."

DEEP DIVE
NOOMF is the opposite of OOMF. It’s commonly used on stan Twitter to talk about someone who doesn’t follow you. It can be used disparagingly or neutrally to refer to someone who isn’t following a tweet’s author or to call out one of their followers to say “not one of my followers (doing X thing).”
just watching noomf embarrass themselves
— elias happily married era (@yrfemmehusband) February 16, 2021
spare 8.4k to oomf and 9.6k to noomf π pic.twitter.com/qayDnmNL1r
— loren π© (@pigzas) February 24, 2021
I GET THE POINT OF USING OOMF IN CONVERSATIONS WITH MOOTS BUT WHAT THE FUCK WHY WOULD YOU USE 'NOOMF' OR 'NON-OOMF'
— deys π₯ okay hi kids (@avocadeys) February 12, 2021