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Phrase(s): cloud up
1. Lit. [for the sky] to get cloudy, as if it were going to rain. • All of a sudden it clouded up and began to rain. • It usually clouds up at the top of the mountain. 2. Fig. [for someone] to grow very sad, as if to cry. • Whenever Mary got homesick, she’d cloud up. She really wanted to go home.
McGrawhill's American Idioms And Phrasal Verbs