keep a straight face, to

keep a straight face

To have an emotionless facial expression, especially in a humorous situation that could easily cause one to laugh. It's so hard to keep a straight face on camera when you have hilarious co-stars like I do.
See also: face, keep, straight
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

keep a straight face

Don't show one's feelings, especially refrain from laughing. For example, The school orchestra played so many wrong notes that I had trouble keeping a straight face . [Late 1800s]
See also: face, keep, straight
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

keep a straight face

COMMON If you keep a straight face, you manage not to laugh or smile. `I don't see that there's anything funny about it,' he said, offended. `Of course there isn't,' she said, trying to keep a straight face. Note: You can also say that you say or do something with a straight face. We've all been practising trying to say we charge $1,000 an hour with a straight face. Note: You can also say that someone is straight-faced. It's the way he tells a joke. He's completely straight-faced and I just fall about laughing.
See also: face, keep, straight
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012

keep a straight face

manage to not show any facial expression, even though you are amused.
See also: face, keep, straight
Farlex Partner Idioms Dictionary © Farlex 2017

keep a straight face, to

Do not burst out laughing; look appropriately serious. This cliché is of fairly recent vintage. Henry Miller used the term in Plexus (1953): “All I felt called upon to do was keep a straight face and pretend that everything was kosher.”
See also: keep, straight
The Dictionary of Clichés by Christine Ammer Copyright © 2013 by Christine Ammer
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