What is You Won't?
1.
Whenever someone says they'll do something, someone else comes back with "You won't!" It's almost like a dare. If the person does said thing, the "You won't"-er usually comes back with something like "OK, so maybe you will."
Commonly used by the surf-bum kids who pioneered such gems of slang like "Dude" and "Sweet".
Person1: Man, every time my math teacher gives me homework, I want to pull a Columbine on her!
Person2: You won't!
(Person1 does. Person2 is arrested as an accessory.)
~OR~
Chemistry Teacher: Now, Hydrogen gas explodes very easily. I could show you a demonstration, but I don't have time.
Pyromaniac Class: You won't! You won't!
Chemistry Teacher: Well, I GUESS we could squeeze it in...
Class: Yay!!!
2.
a prefix to any request of an individual which may affect his gangster if not carried out.
"You won't go to 7-11 and buy a dutch."
"You won't ask that motorist if they have any Grey Poupon."
"You won't drive to Philly at 5am for a cheesesteak."
See
3.
expression used by people, often while playing sports in gym or practicing for their band; challenge of skill;
Guy about to shoot a basketball: I'm gonna make it in!
Other Guy: You won't!
Guy: Say I won't
Other Guy: You won't LOSER
Guy shoots and makes it in
Guy: OH! OH! who da man?
