straight face

WordReference Random House Learner's Dictionary of American English © 2026

ˈstraight ˈface, n. [countable]

1. a plain expression on the face that hides one's true feelings:
   He kept a straight face even though he wanted to laugh.

straight--faced, adj.: 

straight-faced lies.

WordReference Random House Unabridged Dictionary of American English © 2026

straight′ face′, 

1. a serious or impassive facial expression that conceals one's true feelings about something, esp. a desire to laugh.

• 1890–95

straight′-faced′, adj. 
straight-fac•ed•ly  (strāt′fā′sid lē, -fāst′lē), adv. 

Collins Concise English Dictionary © HarperCollins Publishers::

straight face noun

1. a serious facial expression, esp one that conceals the impulse to laugh

ˈstraight-ˈfaced adjective