Basically its a big, strong looking wrestler. Like A-Train, Mat Morgan, Batista, etc. Their size makes them impressive looking just standing there.
The "hoss" reference comes from the old western way of saying horse and was made famous by the 70's western "Bonanza." One of the characters was named Hoss. He was a beefy, burly guy who won every fight because he was so damn big.
Hoss, bitches.