bilabial

n. Sounds articulated with both lips are bilabial. English has three bilabial sounds in its phonemic inventory: [p b m], the consonants in the words Bob, pop, and mom, respectively. Round vowels, like [u] in boot, also involve the lips in their articulation. The lower lip is used to articulate labiodental fricatives like [f v] - the two consonants in the word five - and the labiodental nasal [K], occurring at the end of the first syllable in the word symphony. The upper lip, however, is never used without the lower lip to articulate sounds in natural languages.

- EMF