v. flexed, flex·ing, flex·es
1. To bend (something pliant or elastic).
a. To bend (a joint).
b. To bend (a joint) repeatedly.
a. To contract (a muscle, for example).
b. To move by muscular control: "Sandy flexes his brow characteristically" (Scott Turow).
4. To exhibit or show off the strength of: "They had spent six years since the lightning Six Day War flexing their invincibility" (Howard Kaplan).
To bend: "His hands flexed nervously as he spoke" (Mary McCarthy).
1. Chiefly British Flexible insulated electric cord.
2. The act or an instance of flexing; a bending.
3. Flexibility: a schedule with a lot of flex.
flex (one's) muscles Informal
To exhibit or show off one's strength.
[Latin flectere, flex-, to bend.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 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.