Crabs is a pejorative used to describe incels on wizchan and much more rarely r9k. It is often said to express disgust toward self-identifying incels suggesting they bring each other down, in a, "crabs in a bucket", mentality.
Wizchan has a wordfilter that changes the word incel to crab in any post although the admin insists he chose the word crab at random and it didn't have a deeper meaning.
