Source : Webster's Revised Unabridged Dictionary (1913)

Vernacular \Ver*nac"u*lar\, n.
   The vernacular language; one's mother tongue; often, the
   common forms of expression in a particular locality.

Vernacular \Ver*nac"u*lar\, a. [L. vernaculus born in one's
   house, native, fr. verna a slave born in his master's house,
   a native, probably akin to Skr. vas to dwell, E. was.]
   Belonging to the country of one's birth; one's own by birth
   or nature; native; indigenous; -- now used chiefly of
   language; as, English is our vernacular language. ``A
   vernacular disease.'' --Harvey.

         His skill the vernacular dialect of the Celtic tongue.
                                                  --Fuller.

         Which in our vernacular idiom may be thus interpreted.
                                                  --Pope.

Source : WordNet®

vernacular
     n 1: a characteristic language of a particular group (as among
          thieves); "they don't speak our lingo" [syn: {cant}, {jargon},
           {slang}, {lingo}, {argot}, {patois}]
     2: the everyday speech of the people (as distinguished from
        literary language)

vernacular
     adj : being or characteristic of or appropriate to everyday
           language; "common parlance"; "a vernacular term";
           "vernacular speakers"; "the vulgar tongue of the
           masses"; "the technical and vulgar names for an animal
           species" [syn: {common}, {vulgar}]