There were a bunch of I'm guessing autistic, and certainly sociopathic, weirdos on Reddit who made a subforum for themselves by the name of “incel,” for involuntary celibate. It was dedicated to complaining about how women aren't fornicating with the men in question--which as you know is held up as the standard of how people are supposed to live in the disgusting media--and the problems of immoral modern women who run around sinning with one jock after the other. The irony being of course that they had exactly the same attitude they complained about in women.
They were sick--even by the standards of Reddit--so they got themselves banned. It was one big fantasy about how women are all bad and should be forcibly made to serve the desires of “men” like themselves.
People use incel as an insult with the meaning of a socially inept man who can't get women to sleep with him. About the same as the insult “virgin” which it has mostly replaced. No Christian should speak like that.