Source : Webster's Revised Unabridged Dictionary (1913)

Labial \La"bi*al\, n.
   1. (Phonetics) A letter or character representing an
      articulation or sound formed or uttered chiefly with the
      lips, as {b}, {p}, {w}.

   2. (Mus.) An organ pipe that is furnished with lips; a flue
      pipe.

   3. (Zo["o]l.) One of the scales which border the mouth of a
      fish or reptile.

Labial \La"bi*al\, a. [LL. labialis, fr. L. labium lip: cf. F.
   labial. See {Lip}.]
   1. Of or pertaining to the lips or labia; as, labial veins.

   2. (Mus.) Furnished with lips; as, a labial organ pipe.

   3. (Phonetics)
      (a) Articulated, as a consonant, mainly by the lips, as b,
          p, m, w.
      (b) Modified, as a vowel, by contraction of the lip
          opening, as [=oo] (f[=oo]d), [=o] ([=o]ld), etc., and
          as eu and u in French, and ["o], ["u] in German. See
          Guide to Pronunciation, [sect][sect] 11, 178.

   4. (Zo["o]l.) Of or pertaining to the labium; as, the labial
      palpi of insects. See {Labium}.

Source : WordNet®

labial
     adj 1: of or relating to the lips of the mouth; "labial stops"
     2: relating to or near the female labium

labial
     n : a consonant whose articulation involves movement of the lips
         [syn: {labial consonant}]