labial
Concise Oxford English Dictionary © 2008 Oxford University Press:
labial /ˈleɪbɪəl/
▶adjective
- 1 chiefly Anatomy & Biology relating to the lips or a labium.
- 2 Phonetics (of a consonant) requiring partial or complete closure of the lips (e.g. p or w), or (of a vowel) requiring rounded lips (e.g. oo).
– derivatives
labialize (or labialise) verb,
labially adverb.
labialize (or labialise) verb,
labially adverb.
– origin C16: from med. L. labialis, from L. labium ‘lip’.
'labial' also found in these Oxford entries:

