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.

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

to become thin or thinner; become reduced or diminished (often fol. by down, out, off, etc.)

The crowd is thinning out.