The Collaborative International Dictionary of English v.0.48:

Lesbian \Les"bi*an\ (l[e^]z"b[i^]*an), a.
   1. Of or pertaining to the island anciently called Lesbos,
      now Mitylene, in the Grecian Archipelago.
      [1913 Webster]

   2. Amatory; erotic; -- in allusion to the reputed sensuality
      of the Lesbian people and literature; as, Lesbian novels.
      [archaic]
      [Webster 1913 Suppl.]

   3. Homosexual; -- applied to female homosexuals.
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Lesbian \Les"bi*an\ (l[e^]z"b[i^]*an), n.
   A female homosexual.

   Syn: dyke[vulgar, deprecatory]. [PJC]

WordNet (r) 3.0 (2006):

lesbian
    adj 1: of or relating to or characterized by homosexual
           relations between woman [syn: lesbian, sapphic]
    n 1: a female homosexual [syn: lesbian, tribade, gay
         woman]
    2: a resident of Lesbos

Moby Thesaurus II by Grady Ward, 1.0:

48 Moby Thesaurus words for "lesbian":
   AC-DC, amazon, amphierotic, androgyne, auntie, autoerotic, bi-guy,
   bisexed, bisexual, bull dyke, butch, catamite, chicken, deviant,
   dyke, effeminate, fag, faggot, fairy, femme, flit, fricatrice,
   fruit, gay, gunsel, homo, homoerotic, homophile, homosexual,
   homosexualist, hoyden, invert, mannish, nance, pansy, pathic,
   perverted, punk, queen, queer, romp, sapphic, sapphist, tomboy,
   transvestite, tribade, tribadistic, virago