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.
transitive verb-·lied, -·ly·ing
(comparative willier or more willy, superlative williest or most willy)
- Alternative form of willow.
From Middle English wilÈe, from Old English wiliÄ¡ (“willow"). More at willow.
- (hypocoristic, slang, childish) the penis.
- (UK) a person whom the speaker dislikes.