- Relatively small in extent from one surface to the opposite, usually in the smallest solid dimension: a thin book. (adjective)
- Not great in diameter or cross section; fine: thin wire. (adjective)
- Lean or slender in form, build, or stature. (adjective)
- Not dense or concentrated; sparse: the thin vegetation of the plateau. (adjective)
- More rarefied than normal: thin air. (adjective)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.