Source : Webster's Revised Unabridged Dictionary (1913)

Ectozoon \Ec`to*zo"["o]n\, n.; pl. {Ectozoa}. [NL., fr. Gr. ?
   outside + ? an animal.] (Zo["o]l.)
   See {Epizo["o]n}.

Source : WordNet®

ectozoon
     n : any external parasitic organism (as fleas) [syn: {ectoparasite},
          {ectozoan}, {epizoan}, {epizoon}]