thick / [unvoicedth]ik/ • adj. 1. with opposite sides or surfaces that are a great or relatively great distance apart: thick slices of bread the walls are 5 feet thick. ∎  (of a garment or other knitted or woven item) made of heavy material for warmth or comfort: a thick sweater. ∎  of large diameter: thick metal cables. ∎  (of script or type) consisting of broad lines: a headline in thick black type.2. made up of a large number of things or people close together: his hair was long and thick the road winds through thick forest. ∎  (thick with) densely filled or covered with: the room was thick with smoke| fig. the air was thick with rumors. ∎  (of air, the atmosphere, or an odor carried by them) heavy or dense: a thick odor of dust and perfume. ∎  (of darkness or a substance in the air) so black or dense as to be impossible or difficult to see through: the shore was obscured by thick fog.3. (of a liquid or a semiliquid substance) relatively firm in consistency; not flowing freely: thick mud.4. inf. of low intelligence; stupid: he's a bit thick I've got to shout to get it into your thick head.5. (of a voice) not clear or distinct; hoarse or husky. ∎  (of an accent) very marked and difficult to understand.6. inf. having a very close, friendly relationship: he's very thick with the new boss.• n. (the thick) rare the busiest or most crowded part of something; the middle of something: the thick of battle.• adv. in or with deep, dense, or heavy mass: bread spread thick with butter.PHRASES: be thick on the groundsee ground¹ .a bit thick Brit., inf. unfair or unreasonable.have a thick skinsee skin.thick and fast rapidly and in great numbers. (as) thick as a brick very stupid. (as) thick as thieves inf. (of two or more people) very close or friendly; sharing secrets.through thick and thin under all circumstances, no matter how difficult: they stuck together through thick and thin.DERIVATIVES: thick·ish adj.thick·ly adv. thickly carpeted corridors.