Incel as a term describes something much more specific than “virgin (but they don’t want to be).” That may be the literal meaning of the words, but like, we all know that the Democratic People’s Republic of North Korea is not democratic, people’s, or a republic.
Incel, the way it’s typically used, describes a particular type of person who’s embittered by their long-lasting virginity, and because of that, views most or all members of the opposite sex as lesser than them, believing that they’re in some way owed sex, and have been denied that ‘right.’