mellow out

mellow out idiom
Become genial or pleasant, calm down, relax, as in The teacher mellowed out when they explained what had happened. This expression uses mellow in the sense of “ripening,” with the connotation of softness and sweetness. [Slang; late 1900s]

The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

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