Top definition
The (often surprise) discovery of a penis on a woman who, it transpires, is a transexual or, in the vernacular, a ladyboy.
Hey! Did you hear about Greg last night? He clicked with a Thai girl at the bar and when he got home with her he found she had a filly willy! Dude, was he shocked!
by Hotpepper6005 June 04, 2011
Get the mug
Get a Filly Willy mug for your cousin Callisto.