thin

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Relatively small in extent from one surface to the opposite, usually in the smallest solid dimension.
• adjective Not great in diameter or cross section; fine.
• adjective Having little bodily flesh or fat; lean or slender.
• adjective Not dense or concentrated; sparse.
• adjective More rarefied than normal.
• adjective Flowing with relative ease; not viscous.
• adjective Watery.
• adjective Sparsely supplied or provided; scanty.
• adjective Having a low number of transactions.
• adjective Lacking force or substance; flimsy.
• adjective Lacking resonance or fullness; tinny.
• adjective Lacking radiance or intensity.
• adjective Not having enough photographic density or contrast to make satisfactory prints. Used of a negative.
• adverb In a thin manner.
• adverb So as to be thin.
• transitive & intransitive verb To make or become thin or thinner.

from The Century Dictionary.

• Thinly.
• To make thin.
• To make less dense or compact; make sparse; specifically, to rarefy, as a gas.
• To reduce in consistency or viscosity: said of liquids: as, to thin starch.
• To reduce in strength or richness: as, to thin the blood.
• To make lean or spare.
• To reduce in numbers or frequency.
• To make bare or empty.
• To become thin.
• Very narrow in all diameters; slender; slim; long and fine: as, a thin wire; a thin string.
• Very narrow in one diameter; having the opposite surfaces very near together; having little thickness or depth; not thick; not heavy: as, thin paper; thin boards: opposed to thick.
• Having the constituent parts loose or sparse in arrangement; lacking density, compactness, or luxuriance; rare; specifically, of the air and other gases, rarefied.
• Hence, easily seen through; transparent, literally or figuratively; shallow; flimsy; slight: as, a thin disguise.
• Having slight consistency or viscosity: said of liquids: as, thin syrup; thin gruel.
• Deficient in some characteristic or important ingredient; lacking strength or richness; specifically, of liquors, small: opposed to strong.
• Of sound, lacking in fullness; faint, and often somewhat shrill or metallic in tone.
• Limited in power or capacity; feeble; weak.
• Meager; lean; spare; not plump or fat.
• Limited in quantity or number; small or infrequent; scanty.
• Scantily occupied or furnished; bare; empty: used absolutely or with of.
• Having no depth: said of a school of fish.
• Having insufficient density or contrast to give a good photographic print or a satisfactory image on the screen; weak: said of a negative or a lantern-slide.
• A Middle English form of thine.
• 14. In art, characterized, in composition, by few and widely separated elements, by absence of serious interest, or by lack of body and force in technique.

from the GNU version of the Collaborative International Dictionary of English.

• adverb Not thickly or closely; in a seattered state.
• transitive verb To make thin (in any of the senses of the adjective).
• adjective Having little thickness or extent from one surface to its opposite
• adjective Rare; not dense or thick; -- applied to fluids or soft mixtures.
• adjective Not close; not crowded; not filling the space; not having the individuals of which the thing is composed in a close or compact state; hence, not abundant
• adjective Not full or well grown; wanting in plumpness.