The Collaborative International Dictionary of English v.0.48:

Frigate \Frig"ate\, n. [F. fr['e]gate, It. fregata, prob.
   contracted fr. L. fabricata something constructed or built.
   See Fabricate.]
   1. Originally, a vessel of the Mediterranean propelled by
      sails and by oars. The French, about 1650, transferred the
      name to larger vessels, and by 1750 it had been
      appropriated for a class of war vessels intermediate
      between corvettes and ships of the line. Frigates, from
      about 1750 to 1850, had one full battery deck and, often,
      a spar deck with a lighter battery. They carried sometimes
      as many as fifty guns. After the application of steam to
      navigation steam frigates of largely increased size and
      power were built, and formed the main part of the navies
      of the world till about 1870, when the introduction of
      ironclads superseded them. [Formerly spelled frigat and
      friggot.]
      [1913 Webster]

   2. Any small vessel on the water. [Obs.] --Spenser.
      [1913 Webster]

   Frigate bird (Zool.), a web-footed rapacious bird, of the
      genus Fregata; -- called also man-of-war bird, and
      frigate pelican. Two species are known; that of the
      Southern United States and West Indies is F. aquila.
      They are remarkable for their long wings and powerful
      flight. Their food consists of fish which they obtain by
      robbing gulls, terns, and other birds, of their prey. They
      are related to the pelicans.

   Frigate mackerel (Zool.), an oceanic fish (Auxis Rochei)
      of little or no value as food, often very abundant off the
      coast of the United States.

   Frigate pelican. (Zool.) Same as Frigate bird.
      [1913 Webster]

WordNet (r) 3.0 (2006):

frigate
    n 1: a medium size square-rigged warship of the 18th and 19th
         centuries
    2: a United States warship larger than a destroyer and smaller
       than a cruiser