Either a non-U.S.An. term for a vagina or pussy or a United States of American term for the buttocks or ass. The regional differences are grounds for humo-U-r.
Winston Churchill: Wow! Last night with the wife was fantastic.
Uncle Sam: Yeah? What did you do to her?
Churchill: Well, first I had to suck her fanny...
Sam: Wait! What did you do?
Churchill: I sucked her fanny--I sucked her fanny dry to where there wasn't anything left in there!
Sam: I didn't know you liked to eat shit.
Sam: You ate your wife's ass out dry, as you said. Either that or she had an operation that switched her ass with her pussy.
Churchill: What the hell are you talking about?
(Winston Churchill and Uncle Sam get into a bitch fight.)