Any word beginning with f that is not normally taboo but is considered (often humorously) to be so in the given context.(noun)
To use vulgarities.(verb)
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Use "f-word" in a sentence
"All three lawyers who argued and the justices never used the expletives at the heart of the dispute, but instead referred to the "f-word" or the "s-word.""
"And you've got to give it to a woman who will scream the f-word at a news camera in the middle of a school board meeting."
"By contrast, Western parents have to tiptoe around the issue, talking in terms of "health" and never ever mentioning the f-word, and their kids still end up in therapy for eating disorders and negative self-image."