A frivolous, dim-witted, useless, and/or unintelligent person. I can't believe I got paired with such an airhead for this assignment. He's not going to get any work done at all!
airhead
and airbrain
n. a stupid person. (Someone with air where there should be brains.) Some airbrain put mustard in the ketchup dispenser. Bart seems like such an airhead, but he’s all heart.
airheaded
mod. stupid; giddy. (A head full of air.) You are the most airheaded twit I have ever met!