—adj. 1. having relatively little extent from one surface or side to the opposite; not thick: thin ice. 2. of small cross section in comparison with the length; slender: a thin wire. 3. having little flesh; spare; lean: a thin man. 4. composed of or containing objects, particles, etc., widely separated; sparse: thin vegetation. 5. scant; not abundant or plentiful.
6. of relatively slight consistency or viscosity: thin soup. 7. rarefied, as air.
8. without solidity or substance; flimsy: a very thin plot for such a long book. 9. lacking fullness or volume; weak and shrill: a thin voice. 10. without force or a sincere effort: a thin smile. 11. lacking body, richness, or strength: a thin wine. 12. lacking in chroma; of light tint.
13. Photog.(of a developed negative) lacking in density or contrast through underdevelopment or underexposure.
—adv. 1. in a thin manner.
2. sparsely; not densely.
3. so as to produce something thin: Slice the ham thin.
—v.t. to make thin or thinner (often fol. by down, out, etc.).
—v.i. to become thin or thinner; become reduced or diminished (often fol. by down, out, off, etc.): The crowd is thinning out.