When you are in the shower with a girl and the guy stretches out his nut sack and fills it with water and then the girl drinks out of it.
I was in the shower with my girlfriend and the told me she was thirsty. So I had her bend down and I gave her a Dirty Bird Bath.
by NMBMKBKMBMGB July 23, 2009
Bend he/she over, spread open his/her asshole and slowly urinate into the orifice. He/she then splashes around in the pool of urine in the asshole.
Last night he bent me over and pissed in my asshole and then splashed around in it like it was a dirty birdbath.
by Kammi Kazi November 23, 2006