The Brief: The term Coomer describes a person helplessly addicted to masturbation.

DEEP DIVE
The Coomer character originated on 4chan before spreading to Twitter via the “Coomer Pledge,” a pact in which those who fail No Nut November must change their profile pictures to a caricature of the Coomer.
TAKE THE PLEDGE pic.twitter.com/IGfZ4up4QL
— rolling stone are coomers (@TeapotLad) October 29, 2019
The term “Ok Coomer,” a play on the “Ok Boomer” insult, has become the preferred retort against those who criticize No Nut November for being misogynistic and having far-right roots.
OK coomer https://t.co/9qwcHE4kAo pic.twitter.com/XsA8AHZGl3
— ⌬Coalbol🏴🤟🥶 (@coalbol) November 1, 2019