four-letter word

four-letter word idiom
Any of several short English words that are generally regarded as vulgar or obscene. For example, No four-letter words are permitted in this classroom. This expression is applied mostly to words describing excretory or sexual functions. [First half of 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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