Penis, male sexual organ. This is a phrase that a parent might use to a child, or a girl might use talking to her friend as it is a milder word than penis for example. It is a suitable word to use in polite conversation if it is necessary to use the word penis.
In British English the title of the American film "Free Willy" is very unfortunate.
For example:(parent talking to small child) It's not polite to show your willy in public.
Boys have willies and girls don't.
My ex-boyfriend had a very small willy, so I left him.
W is for willy. W-I-L-L-Y. OK, this is a British middle class slang. Willy, penis, male sexual organ, cock, dick, member and many more. Willy is a phrase that perhaps parents use with children. OK, it's less strong than penis. And notice, this is British and middle class, the phrase, OK. But it's slang. Perhaps you make jokes about getting your willy caught in a door. Ouch! That must really hurt. OK. Or perhaps you say to your ...to a child erm... shake your willy after urinating, or after peeing. OK. It's as I said, it's better, or it's less rude, or it's less strong than many other words and for that reason it's used. So, willy, male sexual organ, penis. So, thanks for watching and I'll see you in another video. Bye for now.