Female version of the bro-fist often used by bitchy females after a rude comment was issued, also used when something funny was said.
Sarah: Did you see that loser Shaun hit on me?"
Jennifer: Yeah i heard you pantsed him and told him to go die, hahah"
Sarah: Bitchfist!"
*Sarah initiates bitch fist by putting out fist*
*Jennifer does the same and hits fists with her*