laugh up one's sleeve

laugh up (one's) sleeve

1. To try to hide that one is laughing at someone else. Ron may seem like a nice guy, but he laughs up his sleeve whenever he's around someone he dislikes. The popular kids laugh up their sleeves every time I walk by—it's so infuriating.
2. To rejoice or be amused secretly and/or contemptuously, as at another's mistakes or misfortunes. Though they are feigning sympathy, I'm sure my colleagues are all laughing up their sleeves at me for being chewed out by the boss. I know it is mean spirited, but I cannot help but laugh up my sleeve when I see someone slip on the icy streets.
See also: laugh, sleeve, up

laugh up one's sleeve

Rejoice or exult secretly, hide one's amusement, as in When she tripped over her bridal train, her sister couldn't help laughing up her sleeve. This expression replaced the earlier laugh in one's sleeve, used by Richard Sheridan in The Rivals (1775): "'Tis false, sir, I know you are laughing in your sleeve." The expression, which alludes to hiding one's laughter in big loose sleeves, was already a proverb in the mid-1500s.
See also: laugh, sleeve, up