thickness

UK: /ˈθɪknɪs/ US: (thik′nis)

WordReference Random House Unabridged Dictionary of American English © 2026

thick•ness  (thik′nis), n. 

1. the state or quality of being thick.
2. Weights and Measures the measure of the smallest dimension of a solid figure:
   a board of two-inch thickness.
3. the thick part or body of something:
   the thickness of the leg.
4. a layer, stratum, or ply:
   three thicknesses of cloth.

v.t. 

5. Weights and Measures to bring (a piece, as a board) to a uniform thickness.

• Middle English thiknesse, Old English thicnes. See thick, -ness bef. 900

Collins Concise English Dictionary © HarperCollins Publishers::

thickness / ˈθɪknɪs/ noun

1. the state or quality of being thick
2. the dimension through an object, as opposed to length or width
3. a layer of something

WordReference Random House Learner's Dictionary of American English © 2026

thick /θɪk/   adj. and adv., -er, -est, n. 
adj. 

1. having a great distance from one surface to the opposite;
   not thin:
   a thick slice of bread.
2. measured between opposite surfaces:
   [after a noun or phrase of measurement] a board one inch thick.
3. made up of objects close together;
   dense: difficult to see through:
   The planes couldn't land in the thick fog.
4. filled or covered:
   [be + ~ + with] The air was thick with tobacco smoke.
5. not clearly pronounced or articulated:
   thick speech.
6. easy to notice;
   obvious:
   I have a thick Russian accent when I speak English.
7. deep or profound:
   thick darkness.
8. intimate;
   close (in friendship):
   thick friends.
9. heavy;
   not easily poured:
   thick soup.
10. mentally slow;
    stupid:
    Sometimes he can be a little thick.

adv. 

11. in a thick manner.
12. close together:
    vines growing thick.
13. so as to produce something thick:
    The cheese was sliced thick.

n. [uncountable]

14. the densest or most crowded part:
    in the thick of the fight.

Idioms

15. thick as thieves, close in friendship;
    very friendly.
16. Idioms through thick and thin, under both favorable and unfavorable conditions;
    faithfully:
    They stayed friends through thick and thin.

thick•ly, adv. 
thick•ness, n. [uncountable]

WordReference Random House Unabridged Dictionary of American English © 2026

thick (thik),  adj., -er, -est, adv., -er, -est, n. 

adj. 

1. having relatively great extent from one surface or side to the opposite;
   not thin:
   a thick slice.
2. measured, as specified, between opposite surfaces, from top to bottom, or in a direction perpendicular to that of the length and breadth;
   (of a solid having three general dimensions) measured across its smallest dimension:
   a board one inch thick.
3. composed of or containing objects, particles, etc., close together;
   dense:
   a thick fog; a thick forest.
4. filled, covered, or abounding (usually fol. by with):
   tables thick with dust.
5. husky or hoarse;
   not distinctly articulated:
   The patient's speech is still quite thick.
6. markedly so (as specified):
   a thick German accent.
7. deep or profound:
   thick darkness.
8. (of a liquid) heavy or viscous:
   a thick syrup.
9. [Informal.] close in friendship;
   intimate.
10. mentally slow;
    stupid;
    dull.
11. disagreeably excessive or exaggerated:
    They thought it a bit thick when he called himself a genius.

adv. 

12. in a thick manner.
13. close together;
    closely packed:
    The roses grew thick along the path.
14. in a manner to produce something thick:
    Slice the cheese thick.
15. lay it on thick, [Informal.] to praise excessively;
    flatter:
    He's laying it on thick because he wants you to do him a favor.

n. 

16. the thickest, densest, or most crowded part:
    in the thick of the fight.
17. through thick and thin, under favorable and unfavorable conditions;
    steadfastly:
    We have been friends for 20 years, through thick and thin.

• bef. 900; (adjective, adjectival and adverb, adverbial) Middle English thikke, Old English thicce; cognate with Dutch dik, German dick; akin to Old Norse thykkr (noun, nominal) Middle English, derivative of the adjective, adjectival

thick′ish, adj. 
thick′ly, adv. 
Synonyms

• 6. strong, pronounced, decided.