The act of putting someone down for having sex with too many people. Normally applied only to women, but can and should be used for men also.
This word has been hijacked by modern "feminists" who think its use only targets women and poorly reflects on all women regardless of sexual orientation, sexual habits, and sexual practices.
Misuse of word is caused by confusion of the meaning of the word "slut".
"Jenny had a train
pulled on her last night by the football team and she loved it! What a piece of nasty crap!"
"You asshole. That's totally acceptable behavior and you're just slut shaming her. You will only hurt her and the rest of womanhood."