Idioms and Phrases with flex one's muscles
flex one's muscles
Show off one's strength or power, as in The boys love flexing their muscles, or The new department head has decided to flex her muscles. [Early 1900s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.