- The definition of a willy is a slang term for a penis.
When you are referring to the genital organ that your boyfriend uses for sex and you want to use a slang term to refer to that male organ, the slang term you would use is an example of willy.
(comparative willier or more willy, superlative williest or most willy)
- Alternative form of willow.
- (hypocoristic, slang, childish) the penis.
- (UK) a person whom the speaker dislikes.