a. The short thick digit of the human hand, next to the index finger and opposable to each of the other four digits.
b. A corresponding digit in other animals, especially primates. Also called pollex.
2. The part of a glove or mitten that covers the thumb.
3. Architecture An ovolo.
v. thumbed, thumb·ing, thumbs
1. To scan (written matter) by turning over pages with or as if with the thumb.
2. To disarrange, soil, or wear by careless or frequent handling.
3. Informal To solicit (a ride) from a passing vehicle by signaling with the thumb.
1. To scan written matter by turning over pages with or as if with the thumb: thumbed through the latest issue of the magazine.
2. Informal To hitchhike.
Lacking physical coordination, skill, or grace; clumsy.
thumb (one's) nose
To express scorn or ridicule, often by placing the thumb on the nose and wiggling the fingers.
under (someone's) thumb
Under the control of someone; subordinate to.
[Middle English, from Old English thūma; see teuə- in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.