My definition is someone who gets high on a daily base, enjoys its, and only sticks to pot.
Ren: nothing got high.
Mel: What else do you have planned.
Ren: ugh maybe get high again.
Mel: Whhat.... Ren your just a pot head.
Ren: SO I LOVE IT HAHA
Pothead: "Yeah sure, you wanna smoke a bowl?"
John: "I dunno man, my throat's been kinda sore lately."
Pothead: "Oh that's ok, a bowl will fix that."
John: "Really? Well I've got this Government test tomorrow too, so I probably shouldn't smoke."
Pothead: "Pot makes studying easier. You'll enjoy the subject more!"
John: "You're full of shit. Next you'll tell me weed can fix my chronic back pain and I should get high before visiting my grandma in the nursing home."
Pothead: "I'm glad you understand now. Got a lighter?"
Pot heads should not be confused with occasional smokers who are still able to function and fulfill their responsibilities and obligations.