NOUN (1)

1. a person who knows only one language;


ADJECTIVE (1)

1. using or knowing only one language;
- Example: "monolingual speakers"
- Example: "a monolingual dictionary"

The Collaborative International Dictionary of English v.0.48:

monolingual \mon`o*lin"gual\ adj.
   Using or knowing only one language; as, monolingual speakers;
   a monolingual dictionary. Opposite of multilingual.
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

monolingual
    adj 1: using or knowing only one language; "monolingual
           speakers"; "a monolingual dictionary" [ant:
           multilingual]
    n 1: a person who knows only one language