A broad-brusher is someone with a bluepilled mentality who unduly makes generalizations about another person or another topic. Broad-brushing can occur in many fields, including about race, about ethnicity, about a gender, about a nationality, and so on. Incelphobes commonly make generalizations about involuntary celibates.
A similar type of behaviour is pigeonholing. To pigeonhole means to narrow the scope of a particular meaning, usually for political propaganda purposed. It is a favorite tactic of the bluepiller. As such, listening to a bluepiller explain the meaning of a word is a big No-No.
On the other hand, blackpillers often make broad-brush generalizations about women.