vulgarism

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Vulgarity.
• noun A crudely indecent word or phrase; an obscenity.
• noun A word, phrase, or manner of expression used chiefly by uneducated people.

from The Century Dictionary.

• noun Coarseness, rudeness, or grossness of manners; vulgarity; commonness.
• noun A phrase or expression used only in common colloquial, especially in coarse, speech.

from the GNU version of the Collaborative International Dictionary of English.

• noun Grossness; rudeness; vulgarity.
• noun A vulgar phrase or expression.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun grammar A word or term that is considered offensive or vulgar.
• noun A spelling, word, or phrase used in common speech that is considered improper or incorrect for formal communication.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the quality of lacking taste and refinement
• noun an offensive or indecent word or phrase