To deliberately substitute a harsh or vulgar word for a mild one; to replace gentle language with crude language.
From heterophemism + -ize (to make or become). Following the standard English pattern of euphemize, this verb form describes the action of performing heterophemisms.
To heterophemize is to do the opposite of what you'd do with a euphemism—instead of softening your language, you're deliberately making it harsher or ruder! It's what happens when someone 'unfilters' on purpose.
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