laugh up one's sleeve

Verb

laugh in one's sleeve (third-person singular simple present laughs in one's sleeve, present participle laughing in one's sleeve, simple past and past participle laughed in one's sleeve)

1. (Canada, US, idiomatic) to laugh in secret or to oneself, usually gloatingly
   • Nixon boastfully called the seven days he spent on the Chinese mainland "the week that changed the world"–without, however, specifying whether the change was for the better or for the worse. The way he humbled himself before Mao Tse-tung and Chou En-lai reminded me of the tribute-bearing foreign...1983, James C. H. Shen, “Beginnings of Endings”, in Robert Myers, editor, The U.S. & Free China: How the U.S. Sold Out Its Ally, Washington, D.C.: Acropolis Books Ltd., →ISBN, →LCCN, →OCLC, page 7