Means sharp, cool, wicked awesome, etc.It's a compliment to call someone or something tuff. Used in S.E. Hintons Tuff book The Outsiders.
Johnny: Man, that is a tough car. Mustangs, huh, they're tuff.
Jen: You know Pat?
Meg: Yeah, he's pretty tuff.
When a animal (or person) is greedy and always in search of more, particularly food.
"Get away Clancey, this is my food! You gravy sucking sled dog."