laugh up sleeve
Also found in: Dictionary, Thesaurus, Medical.
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.
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.