Verb: When a man inserts himself into a full-blown conversation that had previously involved only women, in order to mansplain something related to the topic they're discussing. Often a reflexive reaction to discourse that would pass the Bechdel Test if it were a movie (because it doesn't involve the man who's overhearing it).
Dude, you just mansplainterrupted a League of Women Voters meeting to tell them about the history of suffrage.