it's whenever a hooker and or a loved one with bad yellowish teeth gets a cumshot in the mouth, and then proceeds to slosh it between thier teeth and spits it out, leaving the cum thick and yellow like butter.
"dude, did you see cindy?", "Yeah man that slut had hooker butter all over her shirt"
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi