Wordnet 3.0
NOUN (1)
1. 
 either of two different animal or plant species living in close association but not interdependent; 
ADJECTIVE (1)
1. 
 living in a state of commensalism; 
The Collaborative International Dictionary of English v.0.48:
Commensal \Com*men"sal\, n. [LL. commensalis; L. com- + mensa
   table: cf. F. commensal. Cf. Mensal.]
   1. One who eats at the same table. [Obs.]
      [1913 Webster]
   2. (Zool.) An animal, not truly parasitic, which lives in,
      with, or on, another, partaking usually of the same food.
      Both species may be benefited by the association.
      [1913 Webster]
The Collaborative International Dictionary of English v.0.48:
Commensal \Com*men"sal\, a.
   Having the character of a commensal.
   [1913 Webster]
WordNet (r) 3.0 (2006):
commensal
    adj 1: living in a state of commensalism
    n 1: either of two different animal or plant species living in
         close association but not interdependent
Moby Thesaurus II by Grady Ward, 1.0:
78 Moby Thesaurus words for "commensal":
   cannibal, cannibalistic, carnivorous, coacting, coactive,
   coadjutant, coadjuvant, coefficient, collaborative, collective,
   collectivist, collectivistic, collusive, combined, common,
   communal, communalist, communalistic, communist, communistic,
   communitarian, concerted, concordant, concurrent, concurring,
   conniving, cooperant, cooperating, cooperative, dietetic, dining,
   eating, ecological, ecotopic, ecumenic, feeding, fellow,
   flesh-eating, fruitarian, gastronomic, gluttonous, grain-eating,
   graminivorous, granivorous, grass-eating, harmonious, harmonized,
   herbivorous, insect-eating, insectivorous, joint, lactovegetarian,
   man-eating, meat-eating, mensal, mutual, noncompetitive,
   nourishing, nutritious, omnivorous, omophagous, pantophagous,
   parasitic, phytivorous, phytophagous, plant-eating, postprandial,
   prandial, predacious, preprandial, reciprocal, symbiotic,
   synergetic, synergic, synergistic, uncompetitive, vegetable-eating,
   vegetarian