Wiktionary
fist-fuck
n. (context vulgar slang English) sexual practice in which a (fisted) hand is inserted and moved in, around, or out vagina or rectum in a vigorous manner. vb. (context vulgar English) to insert and remove and move a (fisted) hand in someone's vagina or rectum vigorously
Usage examples of "fist-fuck".
It's like being fist-fucked in the cunt and the asshole simultaneously, an intensity almost too great to bear: "they were practically holding hands inside her.