1) The leader or authority in a group, especially in a group of friends.
2) 2007 Film "Alpha Dog": Johnny Truelove is an Alpha Dog
"Just like how a country has a president, a clique has an Alpha Dog."
1. The leader of a pack that rolls several dogs deep.
2. No leash can hold him, and his tail wags for no one.
3. Alpha Dog's bark is in equal proportion to his bite.
He's got all the bitches- he's the Alpha Dog.