The private parts of a woman who has already had sexual intercourse with someone else
I had sex with Mary after the party, but I don't normally want a buttered bun.
by Tom June 06, 2003
Rolling back to the 1970's joy of sex book,a buttered bun is the highest bond between two male friends. To have sex with a woman, cum inside her, and have the other male have sex with her right after him and let his cum get all over his penis.
Oh, here man, I got this woman all buttered up for ya...
by bonneville babe February 08, 2005