1. an ugly girl who wears too much make-up. extremely skinny. for some reason, alot of guys think she's hot when actually she needs a paper bag. she thinks she's soo cool, but most people hate her. has a reputation for being a whore. totally two-faced and thinks she is the shit. posts 9,000 pictures of herself on photobucket that all looks the same. uses the word "bestie" instead of best friend wayyyy too much.
2. a nickname for the name madison. other ways are maddie, madi, mady, maddi.
3. long story short, just a whore who you shouldn't waste your time with who is popular for no reason.
1. guy: damn, that girl is finee!
girl: what? her? oh please, she's a maddy.
2. person: what other names do you go by instead of madison
maddy: my friends call me maddy.
3. girl 1: she's so cool, i wanna be just like her.
girl 2: yeah, right. she's a maddy.