laugh up your sleeve
成語所屬單字sleeve
laugh up your sleeve — 慣用語
1. to be secretly amused about something while appearing serious on the outside.
1.慣用語
釋義
暗笑；偷笑
to be secretly amused about something while appearing serious on the outside.
例句
When the boss tripped over the cable, Tyler laughed up his sleeve while helping him up with a straight face.
The students thought the teacher had not noticed their prank, but she was laughing up her sleeve the whole time.