Wordnet 3.0
ADJECTIVE (1)
1. 
 (used of relationships and of individuals) having one mate; 
- Example: "monogamous marriage"- Example: "monogamous for life"
The Collaborative International Dictionary of English v.0.48:
Monogamous \Mo*nog"a*mous\, a. [L. monogamus having but one
   wife, Gr. ?; mo`nos single + ? marriage.]
   1. Upholding, or practicing, monogamy.
      [1913 Webster]
   2. (Bot.) Same as Monogamian.
      [1913 Webster]
   3. (Zool.) Mating with but one of the opposite sex; -- said
      of birds and mammals.
      [1913 Webster]
WordNet (r) 3.0 (2006):
monogamous
    adj 1: (used of relationships and of individuals) having one
           mate; "monogamous marriage"; "monogamous for life" [ant:
           polygamous]