The Collaborative International Dictionary of English v.0.48:

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.
      [1913 Webster]

   2. (Mus.) Furnished with lips; as, a labial organ pipe.
      [1913 Webster]

   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.
          [1913 Webster]

   4. (Zool.) Of or pertaining to the labium; as, the labial
      palpi of insects. See Labium.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

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.
      [1913 Webster]

   2. (Mus.) An organ pipe that is furnished with lips; a flue
      pipe.
      [1913 Webster]

   3. (Zool.) One of the scales which border the mouth of a fish
      or reptile.
      [1913 Webster]

WordNet (r) 3.0 (2006):

labial
    adj 1: of or relating to the lips of the mouth; "labial stops"
    2: relating to or near the female labium
    n 1: a consonant whose articulation involves movement of the
         lips [syn: labial consonant, labial]

Moby Thesaurus II by Grady Ward, 1.0:

127 Moby Thesaurus words for "labial":
   accented, allophone, alveolar, apical, apico-alveolar,
   apico-dental, articulated, articulation, aspiration, assimilated,
   assimilation, back, barytone, bilabial, broad, cacuminal, central,
   cerebral, check, checked, close, consonant, consonantal,
   continuant, dental, diphthong, dissimilated, dissimilation, dorsal,
   epenthetic vowel, explosive, flat, front, glide, glossal, glottal,
   glottalization, guttural, hard, heavy, high, intonated,
   labialization, labiate, labiodental, labiovelar, laryngeal,
   lateral, lax, light, lingual, lipped, liquid, low,
   manner of articulation, mid, modification, monophthong,
   monophthongal, morphophoneme, mute, muted, narrow, nasal,
   nasalized, occlusive, open, oxytone, palatal, palatalized,
   parasitic vowel, peak, pharyngeal, pharyngealization,
   pharyngealized, phone, phoneme, phonemic, phonetic, phonic, pitch,
   pitched, plosive, posttonic, prothetic vowel, retroflex, rounded,
   segmental phoneme, semivowel, soft, sonant, sonority, speech sound,
   stop, stopped, stressed, strong, surd, syllabic, syllabic nucleus,
   syllabic peak, syllable, tense, thick, throaty, tonal, tonic,
   transition sound, triphthong, twangy, unaccented, unrounded,
   unstressed, velar, vocable, vocalic, vocoid, voice, voiced,
   voiced sound, voiceless, voiceless sound, voicing, vowel,
   vowellike, weak, wide