Laugh up one’s sleeve

Laugh up one’s sleeve is an idiom. An idiom is a commonly used word, group of words, or phrase that has a figurative meaning that is not easily deduced from its literal definition. Often using descriptive imagery or metaphors, common idioms are words and phrases used in the English language in order to convey a […]
from Grammarist
https://grammarist.com/idiom/laugh-up-ones-sleeve/