Best definition
you dog
a phrase said to someone who is secretly deceptive

You hooked up with Emma behind her guy’s back?! You dog!
you dog: define #2
You Dog!
Commonly used to refer to one’s actions as that of the basic instincts of the Canine family.

Suggesting that their actions mimic the basic of doing whatever it takes to acquire companionship, food, drinks or reproduction.

John: “Hey I heard you went to a party last night ate all their food and went home with Sarah”

Jake: “Haha yeah”

John: “You dog!!”