What it means
Dirty laundry is the private, embarrassing or shameful matters of a person, family or group, the squabbles and scandals best kept out of sight. To air your dirty laundry in public is to let everyone see those grubby secrets, washing the soiled linen where all can watch. The image is of the stained washing you would never hang on the line for the neighbours to gawp at.
Usage examples
"Let us not air our dirty laundry in front of the guests."
"They aired all their dirty laundry in a very public and very messy divorce."
"She aired the family's dirty laundry on national television and her relatives haven't spoken to her since."
"I don't want to discuss the divorce at the office Christmas party, no point in hanging out the dirty laundry."
Where it comes from
From the older idiom "to wash one's dirty linen in public", documented in English from the early 19th century and itself a translation of the French "laver son linge sale en famille" attributed to Napoleon. The American version swapped linen for laundry as the household vocabulary modernised. The image is the same: shameful private matters should stay behind closed doors, not flap in the wind for the neighbours to see.
Other ways to say it
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