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2.
Acting like a combination of Rainman (Dustin Hoffman) and a Retard joined together.
Kayne is such a Raintard

or

did you see that guy Joe, he is acting like a complete raintard

Emma always says when you act like a rainman, you are a really a raintard, and they always think its their cousin fault!
by elwing* August 30, 2011
 
1.
The act of driving like a retard when it starts to rain
The guy in front of me is driving like a total raintard
by Chilton Burr July 05, 2005