The Collaborative International Dictionary of English v.0.48:

Oasis \O"as*is\ ([=o]"[.a]*s[i^]s or [-o]*[=a]"s[i^]s; 277), n.;
   pl. Oases (-s[=e]z). [L., fr. Gr. 'o`asis; cf. Copt.
   ouahe.]
   A fertile or green spot in a waste or desert, esp. in a sandy
   desert, where the water table approaches the surface.
   [WordNet sense 1] "The Arab does not love the desert; the
   Arab loves the oasis and green fields."
   [1913 Webster]

   2. Hence: (fig.) Any refuge from a prevailing stressful,
      unpleasant, or annoying situation. [WordNet sense 2 & 3]

   Syn: haven.
        [PJC]

              My one oasis in the dust and drouth
              Of city life.                       --Tennyson.
        [1913 Webster]