What does "labial" mean?

Additional senses

1. 2.(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 (food), o (old), etc., and as eu and u in French, and ö, ü in German. See Guide to Pronunciation, 4. (Zoöl.) Of or pertaining to the labium; as, the labial palpi of insects. See Labium.
2. 3.(Phonetics) A letter or character representing an articulation or sound formed or uttered chiefly with the lips, as b, p, w.
3. 4.(Mus.) An organ pipe that is furnished with lips; a flue pipe.
4. 5.(Zoöl.) One of the scales which border the mouth of a fish or reptile.