mellow out

mellow out

1. To relax; to calm down. I don't think he has mellowed out yet—I can still hear him yelling.
2. To cause someone to relax; to calm someone down. In this usage, a noun or pronoun can be used between "mellow" and "out." If the baby's crying, try putting her in her swing—that usually mellows her out.
3. To make something less bold in appearance. In this usage, a noun or pronoun can be used between "mellow" and "out." My hair is too dark right now—I think I need some highlights to mellow it out.
See also: mellow, out
Farlex Dictionary of Idioms.

mellow out

 
1. to become less angry. When you mellow out, maybe we can talk. Come on, man, stop yelling and mellow out!
2. to become generally more relaxed. Gary was nearly forty before he started to mellow out a little and take life less seriously. After his illness, he mellowed out and seemed more glad to be alive.
See also: mellow, out
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

mellow out

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]
See also: mellow, out
The American Heritage® Dictionary of Idioms by Christine Ammer.

mellow out

v. Slang
1. To make someone relax; cause someone to become more genial and pleasant: A nice cool drink would mellow me out right now. A nap might mellow out the kids.
2. To relax; become genial and pleasant: Hey, don't get so upset; just mellow out! We stayed at home and mellowed out all day.
3. To make something less intense or less striking: I added some white to the paint to mellow the color out a little bit. We added candles to mellow out the atmosphere.
See also: mellow, out
The American Heritage® Dictionary of Phrasal Verbs.

mellow out

1. in. to calm down; to get less angry. When you mellow out, maybe we can talk.
2. in. to become generally more relaxed; to grow less contentious. After his illness, he mellowed out and seemed more glad to be alive.
See also: mellow, out
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions
See also:
  • calm your tits
  • cooler heads will prevail
  • (someone) needs to take several seats
  • cool, calm, and collected
  • even keel
  • keel
  • beg for
  • beg for (someone or something)
  • calm before the storm, the
  • the calm before the storm