laugh up sleeve

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laugh up (one's) sleeve

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.
See also: laugh, sleeve, up

laugh up one's sleeve

to laugh secretly; to laugh quietly to oneself. Jane looked very serious, but I knew she was laughing up her sleeve. I told Sally that her dress was darling, but I was laughing up my sleeve because her dress was too small.
See also: laugh, sleeve, up