1. A tendon.
2. Vigorous strength; muscular power.
3. often sinews The source or mainstay of vitality and strength: "Good company and good discourse are the very sinews of virtue" (Izaak Walton).
tr.v. sin·ewed, sin·ew·ing, sin·ews
To strengthen with or as if with sinews.
[Middle English sinewe, from Old English sinewe, oblique form of seonu, sinu.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
The American Heritage Dictionary Blog
Check out our blog, updated regularly, for new words and revised definitions, interesting images from the 5th edition, discussions of usage, and more.