The approximate 2 - 10 seconds of immense pain inside of a female's anus that comes and goes without warning. It feels like - more or less - a knife in one's ass.
Girl 1: *starts to wince in pain whilst squirming in chair*
Girl 2: Are you alright?!
Girl 1: *stops* Yeah, I just had a massive case of knife ass
Girl 2: Aw yeah I hate that
Girl 2: Are you alright?!
Girl 1: *stops* Yeah, I just had a massive case of knife ass
Girl 2: Aw yeah I hate that
by deuxgatos January 21, 2011
Get the knife assmug. by DayDay January 4, 2004
Get the Knife Yo Assmug. by Slyder February 17, 2005
Get the ass knifemug. by bob the reindeer knife masacre September 30, 2013
Get the big ass knifemug.