An asstoo is a tattoo that someone gets on their rear end. It is much like a tramp stamp but on the ass.
by hannahhairplane February 09, 2010
by Joe Kicks Your Ass June 28, 2006
Hey Wes, you got to sit down for this. We got drunk at the rugby game and ended up getting asstoo's.
by ALexfromradford October 05, 2009
by pv123 July 20, 2008