a volatile liquid, as turpentine, used to dilute paint, varnish, rubber cement, etc., to the desired or proper consistency.
a person who adds thinners to paints, varnishes, etc.
a person who specializes in weeding plants, pruning shrubbery, thinning fruit, etc.

Origin of thinner

First recorded in 1825–35; thin + -er1




comparative of thin.



adjective, thin·ner, thin·nest.

having relatively little extent from one surface or side to the opposite; not thick: thin ice.
of small cross section in comparison with the length; slender: a thin wire.
having little flesh; spare; lean: a thin man.
composed of or containing objects, particles, etc., widely separated; sparse: thin vegetation.
scant; not abundant or plentiful.
of relatively slight consistency or viscosity: thin soup.
rarefied, as air.
without solidity or substance; flimsy: a very thin plot for such a long book.
lacking fullness or volume; weak and shrill: a thin voice.
without force or a sincere effort: a thin smile.
lacking body, richness, or strength: a thin wine.
lacking in chroma; of light tint.
Photography. (of a developed negative) lacking in density or contrast through underdevelopment or underexposure.


in a thin manner.
sparsely; not densely.
so as to produce something thin: Slice the ham thin.

verb (used with object), thinned, thin·ning.

to make thin or thinner (often followed by down, out, etc.).

verb (used without object), thinned, thin·ning.

to become thin or thinner; become reduced or diminished (often followed by down, out, off, etc.): The crowd is thinning out.

Origin of thin

before 900; (adj. and adv.) Middle English thyn(ne), Old English thynne; cognate with Dutch dun, German dünn, Old Norse thunnr; (v.) Middle English thynnen, Old English thynnian, derivative of the adj.; compare Middle Dutch dunnen, Old Norse thynna; akin to Old Irish tana, Latin tenuis thin, Greek tany- long
Related formsthin·ly, adverbthin·ness, nouno·ver·thin, adjectiveo·ver·thin·ly, adverbo·ver·thin·ness, nounself-thin·ning, adjectivesu·per·thin, adjectiveun·thinned, adjectiveun·thin·ning, adjective

Synonyms for thin

3. slim, slender, skinny, lank, scrawny. Thin, gaunt, lean, spare agree in referring to one having little flesh. Thin applies often to one in an unnaturally reduced state, as from sickness, overwork, lack of food, or the like: a thin, dirty little waif. Gaunt suggests the angularity of bones prominently displayed in a thin face and body: to look ill and gaunt. Lean usually applies to a person or animal that is naturally thin: looking lean but healthy after an outdoor vacation. Spare implies a muscular leanness with no diminution of vitality: Lincoln was spare in body. 5. meager. 8. weak. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for thinner

Contemporary Examples of thinner

Historical Examples of thinner

British Dictionary definitions for thinner



(often plural, functioning as singular) a solvent, such as turpentine, added to paint or varnish to dilute it, reduce its opacity or viscosity, or increase its penetration into the ground


adjective thinner or thinnest

of relatively small extent from one side or surface to the other; fine or narrow
slim or lean
sparsely placed; meagrethin hair
of relatively low density or viscositya thin liquid
weak; poor; insufficienta thin disguise
(of a photographic negative) having low density, usually insufficient to produce a satisfactory positive
mountaineering a climb or pitch on which the holds are few and small
thin on the ground few in number; scarce


in order to produce something thinto cut bread thin

verb thins, thinning or thinned

to make or become thin or sparse
Derived Formsthinly, adverbthinness, noun

Word Origin for thin

Old English thynne; related to Old Frisian thenne, Old Saxon, Old High German thunni, Old Norse thunnr, Latin tenuis thin, Greek teinein to stretch
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for thinner

liquid used to dilute paint, ink, etc., 1904, agent noun from thin (v.).



Old English þynne "narrow, lean, scanty," from Proto-Germanic *thunnuz, *thunw- (cf. West Frisian ten, Middle Low German dunne, Dutch dun, Old High German dunni, German dünn, Old Norse þunnr), from PIE *tnus-, *tnwi-, from weak grade of root *ten- "stretch" (cf. Latin tenuis "thin, slender;" see tenet).

These our actors ... were all Spirits, and Are melted into Ayre, into thin Ayre. [Shakespeare, "The Tempest," IV.i.150, 1610]

Thin-skinned is attested from 1590s; the figurative sense of "touchy" is from 1670s.



Old English þynnian "to make thin" (cf. German dünnen, Dutch dunnen), from thin (adj.). Intransitive sense of "to become less numerous" is attested from 1743; that of "to become thinner" is recorded from 1804. Related: Thinned; thinning.

Online Etymology Dictionary, © 2010 Douglas Harper

Idioms and Phrases with thinner


In addition to the idioms beginning with thin

  • thin as a rail
  • thin edge of the wedge
  • thing or two
  • things are looking up
  • thin on top

also see:

  • into thin air
  • on thin ice
  • spread oneself too thin
  • through thick and thin
  • wear thin
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.