Source : Webster's Revised Unabridged Dictionary (1913)

Kingbird \King"bird\ (-b[~e]rd), n. (Zo["o]l.)
   1. A small American bird ({Tyrannus tyrannus}, or {T.
      Carolinensis}), noted for its courage in attacking larger
      birds, even hawks and eagles, especially when they
      approach its nest in the breeding season. It is a typical
      tyrant flycatcher, taking various insects upon the wing.
      It is dark ash above, and blackish on the head and tail.
      The quills and wing coverts are whitish at the edges. It
      is white beneath, with a white terminal band on the tail.
      The feathers on the head of the adults show a bright
      orange basal spot when erected. Called also {bee bird},
      and {bee martin}. Several Southern and Western species of
      {Tyrannus} are also called king birds.

   2. The king tody. See under {King}.

Source : WordNet®

Tyrannus tyrannus
     n : large American flycatcher [syn: {kingbird}]