NOUN (1)

1. a consonant that is articulated using both lips; /p/ or /b/ or /w/;


ADJECTIVE (1)

1. of or relating to or being a speech sound that is articulated using both lips;
- Example: "bilabial fricatives"

The Collaborative International Dictionary of English v.0.48:

bilabial \bi*la"bi*al\ adj. (Linguistics)
   produced using both lips; -- said of a consonant. As,
   bilabial fricatives. See labial, adj. and {bilabial, n.
   [PJC]

The Collaborative International Dictionary of English v.0.48:

bilabial \bi*la"bi*al\ n. (Linguistics)
   a consonant that is articulated using both lips, as p or b or
   w.
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

bilabial
    adj 1: of or relating to or being a speech sound that is
           articulated using both lips; "bilabial fricatives"
    n 1: a consonant that is articulated using both lips; /p/ or /b/
         or /w/