The Collaborative International Dictionary of English v.0.48:

oecology \oe*col"o*gy\ ([-e]*k[o^]l"[-o]*j[y^]), n. [Gr. o'i^kos
   house + -logy.] (Biol.)
   The various relations of animals and plants to one another
   and to the outer world; -- now more commonly spelled
   ecology. [Also spelled ecology.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

ecology \ecology\ ([-e]*k[o^]l"[-o]*j[y^]), n. [Gr. o'i^kos
   house + -logy.] (Biol.)
   the branch of biology concerned with the various relations of
   animals and plants to one another and to their surrounding
   environment.
   [PJC]

WordNet (r) 3.0 (2006):

ecology
    n 1: the environment as it relates to living organisms; "it
         changed the ecology of the island"
    2: the branch of biology concerned with the relations between
       organisms and their environment [syn: ecology, bionomics,
       environmental science]