In recent internet slang, the term "incel" means "involuntary celibate", and is usually used to describe men who spend all their time online on platforms such as 4chan and Discord and consider it "socializing". The poster-boy incel is the classic obese neckbeard with a graphic tee, greasy hair, and a fedora. (Not to be confused with the "Discord admin", though the two often overlap.) The idea, however, is lack of ability to acquire a romantic or sexual relationship because the individual is so socially repulsive or poorly socialized; therefore, incels come in all shapes and sizes. You can't be an incel so long as you're a volcel, so a vow of celibacy can be a great barrier between you and the dread of social repugnance
I'm not a very judgmental person, and I would say I'm less condescending than most, but there have been a handful of people that I've met and just known immediately that the person screams incel all over. Not to say that they're unworthy of love or happiness, everyone needs social support and intimacy of some sort, but some people just don't have it I guess.