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1.
1.A Pit Bull that has what it takes to not only fight but win.
2.Any hunting dog that is willing to risk life to hunt hold/kill a large or small animal even if it is much larger then himself.
That dog went off the chain 3x and blew thru all 3 dogs it went up with that's a game dog you got there.
by Paul A. Rodriguez July 13, 2007
 
2.
Someone who is stupid or dumb, or unwilling to do fun activities. Also known as a gamebo.
Guy 1: "Hey man wanna go to Jimmys house and smoke some weed?"
Guy 2: "Na man I don't wanna go."
Guy 1: "Dood, don't be such a gamedog!"
by ImNotAGamedog January 11, 2010