when your penis shrinks after taking cocaine or speed
I got really bad billy willy last night. did you?
by polsky November 23, 2007
1 more definition
billy willy is when your dick is so small and unfunctional because the "whizz" (cockney rhyming slang) "billy whizz" = speed has done what it enevitably WILL do to your bulk of your manhood :D
"oh fuck love, i got billy willy"
by Jobie1 ;) October 24, 2004