Literally "good vagina". A term used to describe a girl who is good in bed, or more loosely, a girl one wishes to fuck. Commonly used by teenage boys to describe girls that they wish they had had sex with, but who are in reality way out of their league.
Tom: How hot is Jane?
Sam: Yeah she's mad box.
Tom: Have you been there?
Sam: Nah, I wish.
When you are having continued success with ladies.
Dude, I've been crushing mad box lately must be this new aftershave.
Very mad, but typically refers to someone in the public eye. Of course, as the very idea of putting frogs in a box is eccentric to say the least, one who is very mad can be said to be; As mad as a box of frogs
That Ronan Keating - He's as mad a s a box of frogs.
to be out your fucking tree,a coplete fruit loop
president bush is as mad as a box of frogs