A vulgarism (from Latin vulgus, the "mean folk"), also called scurrility, is a colloquialism of a low or unrefined character, which substitutes a coarse, indecorous word where the context might lead the reader to expect a more refined expression. For example the term "the tits on Botticelli's Venus" is a vulgarism. Vulgarisms are assumed to be associated with low and coarse motivations that were stereotypically supposed to be naturally endemic to the 'meaner classes', who were not moved by 'higher' motives like fame for posterity and honor among peers—motives that were alleged to move the literate classes. Thus the concept of vulgarism carries cultural freight from the outset, and from some social and religious perspectives it does not genuinely exist, or—and perhaps this amounts to the same thing—ought not to exist.

More broadly, vulgarity generally has a social and moral component. Whether deliberate or accidental, the substitution of a commonplace word that is not a euphemism draws attention to what may be a speaker's high-toned moral superiority or sophistication but a fatal flaw in the usage often reveals that the speaker's ambitions are not based in reality. Vulgarisms therefore highlight the pretentious, showing people that lay unwarranted claim to social graces and education and attempt to inflate their status through the use of language they either cannot control or do not understand.