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2.
a smile on a person with braces
I think he would get more compliments if he didn't have that tin grin.
by The Return of Light Joker January 18, 2010
 
1.
One who has metal in their mouth.
Commonly referred to as "braces"
"Dat bitch is a tin grin!
lolz"
by BUBBASPARKZZZ October 21, 2007