Someone who believes (1) any problem can be fixed by smoking marijuana, and (2) any activity is more enjoyable whilst stoned.
John: "Hey man, wanna hang out?"
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?"