mean business

mean business idiom
Be in earnest. For example, He really means business with this deadline. This idiom uses business in the sense of “a serious endeavor.” [Mid-1800s]

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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