Meaning of the word "laugh up your sleeve" in English

What does "laugh up your sleeve" mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

laugh up your sleeve

US /læf ʌp jʊər sliːv/
UK /lɑːf ʌp jɔː sliːv/
"laugh up your sleeve" picture

Idiom

to be secretly amused about something, often at someone else's expense

Example:
She tried to keep a straight face, but I could tell she was laughing up her sleeve.
The politician pretended to be concerned, but everyone knew he was laughing up his sleeve at the public's gullibility.