vernacular

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

• noun The everyday language spoken by a people as distinguished from the literary language.
• noun A variety of such everyday language specific to a social group or region.
• noun The specialized vocabulary of a particular trade, profession, or group.
• noun The common, nonscientific name of a plant or animal.
• adjective Native to or commonly spoken by the members of a particular country or region.
• adjective Using the native language of a region, especially as distinct from the literary language.
• adjective Relating to or expressed in the native language or dialect.
• adjective Of or being an indigenous building style using local materials and traditional methods of construction and ornament, especially as distinguished from academic or historical architectural styles.
• adjective Occurring or existing in a particular locality; endemic.
• adjective Relating to or designating the common, nonscientific name of a biological species.

from The Century Dictionary.

• Native; indigenous; belonging to the country of one's birth; belonging to the speech that one naturally acquires: as, English is our vernacular language. The word is always, or almost always, used of the native language or ordinary idiom of a place.
• Hence, specifically, characteristic of a locality: as, vernacular architecture.
• noun One's mother-tongue; the native idiom of a place; by extension, the language of a particular calling.

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

• adjective Belonging to the country of one's birth; one's own by birth or nature; native; indigenous; -- now used chiefly of language.
• noun The vernacular language; one's mother tongue; often, the common forms of expression in a particular locality, opposed to literary or learned forms.

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

• noun The language of a people, a national language.
• noun Everyday speech, including colloquialisms, as opposed to literary or liturgical language.
• noun Language unique to a particular group of people; jargon, argot.
• noun Roman Catholicism, uncountable The indigenous language of a people, into which the words of the Mass are translated.
• adjective Of or pertaining to everyday language.

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

• noun a characteristic language of a particular group (as among thieves)
• adjective being or characteristic of or appropriate to everyday language
• noun the everyday speech of the people (as distinguished from literary language)