bilabial vs labial

bilabial and labial both are nouns.

Word	Noun	Adjective	Verb	Adverb
bilabial	Yes	Yes	No	No
labial	Yes	Yes	No	No

As nouns, labial is a hypernym of bilabial; that is, labial is a word with a broader meaning than bilabial:

bilabial: a consonant that is articulated using both lips; /p/ or /b/ or /w/
labial: a consonant whose articulation involves movement of the lips

Other hypernyms of bilabial include labial consonant.

bilabial (noun)	labial (noun)
a consonant that is articulated using both lips; /p/ or /b/ or /w/	a consonant whose articulation involves movement of the lips

bilabial (adjective)	labial (adjective)
of or relating to or being a speech sound that is articulated using both lips	relating to or near the female labium
	of or relating to the lips of the mouth