Having extra rough sex with someone as a means to get back at that person
ex. 2: That bitch was mean all day, but she wanted sex later that night. So i grudge fucked her.
1: Fucking someone who you really dislike but would like to punish through sexual intercourse (often a celebrity and often in an aggressive manner).
2: Fucking someone to get back at someone else (usually someone related through blood, friendship, work or sexual relations).
Grudge fuck example 2:
Your ex-girlfriend’s really hot sister
Your boss’ husband
Guy 2: "That sucks! Did you dump her?"
Guy 1: "Sure did, but I grudge fucked that slut first. She won't be able to walk straight for a week."