1 definition by Eric Burns Red
When a man (or woman) inserts their fist into a woman's vagina or anus (also could be a male's anus) and proceeds to violently shake them, while still inside, potentially causing extreme vaginal or anal trauma and/or Downs' Syndrome.
Samantha: Did you hear about Jeni? I heard Alex gave her a gnarly Irish Jackhammer!
Ryan: No shit! What a fucking whore!
Ryan: No shit! What a fucking whore!
by Eric Burns Red June 4, 2010