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]

Words nearby keep a straight face

keep, keep a civil tongue in one's head, keep a low profile, keep a sharp lookout, keep a stiff upper lip, keep a straight face, keep a weather eye out, keep abreast of, keep after, keep an eye on, keep an eye out for