Meaning of “thick” - Learner’s Dictionary

thick

adjective uk us /θɪk/
DISTANCE

B1 Something that is thick is larger than usual between its opposite sides:

a thick slice of meat
a thick layer of snow
10cm/2m, etc thick

B1 being 10cm/2m, etc thick:

a piece of wood 2cm thick
LARGE AMOUNT

B1 growing very close together and in large amounts:

thick, dark hair
SMOKE

B2 Thick smoke, cloud, or fog is difficult to see through:

Thick, black smoke was pouring out of the chimney.
LIQUID

A thick substance or liquid has very little water in it and does not flow easily:

Stir the sauce over a low heat until thick.
STUPID UK informal

not intelligent

be thick with sth

If something is thick with a particular substance, it is covered in or full of that substance:

The air was thick with petrol fumes.

(Definition of “thick adjective” from the Cambridge Learner’s Dictionary © Cambridge University Press)