a thick head

thick head

1. An inability to retain information or understand instructions. He repeated the directions twice, but I just couldn't get it through my thick head.
2. A sore head and unclear thoughts resulting from being sick or having drunk too much alcohol the night before. I couldn't concentrate because of the thick head my sinus infection was giving me. We all came in with thick heads the day after the staff Christmas party, so no one was really working too hard.
3. Of beer, a thick, rich foam produced upon being poured into a glass. I've personally never understood the appeal of drinking beers with thick heads. It just seems like a waste of space in the glass to me.
See also: head, thick
Farlex Dictionary of Idioms.

a thick ˈhead

(informal) a physical condition in which your head is painful or you cannot think clearly as a result of an illness or of drinking too much alcohol: I’ve got a really thick head this morning. OPPOSITE: have/keep a clear head
See also: head, thick
Farlex Partner Idioms Dictionary
See also:
  • thick head
  • conform with
  • conform with (something)
  • be quick on the uptake
  • male blindness
  • on the uptake
  • quick on the uptake
  • you can't miss it
  • garbage in, garbage out
  • from here on