Source : Webster's Revised Unabridged Dictionary (1913)

Insessor \In*ses"sor\, n.; pl. {Insessores}. [See {Insessores}.]
   (Zo["o]l.)
   One of the Insessores. The group includes most of the common
   singing birds.

Insessores \In`ses*so"res\, n. pl. [NL., fr. L. insessor, lit.,
   one who sits down, fr. incidere. See {Insession}.] (Zo["o]l.)
   An order of birds, formerly established to include the
   perching birds, but now generally regarded as an artificial
   group.

Source : WordNet®

Insessores
     n : a bird with feet adapted for perching (as on tree branches);
         this order is now generally abandoned by taxonomists
         [syn: {order Insessores}, {perching bird}, {percher}]