Source : Webster's Revised Unabridged Dictionary (1913)

Pirate \Pi"rate\, n. [L. pirata, Gr. ?, fr. ? to attempt,
   undertake, from making attempts or attacks on ships, ? an
   attempt, trial; akin to E. peril: cf. F. pirate. See
   {Peril}.]
   1. A robber on the high seas; one who by open violence takes
      the property of another on the high seas; especially, one
      who makes it his business to cruise for robbery or
      plunder; a freebooter on the seas; also, one who steals in
      a harbor.

   2. An armed ship or vessel which sails without a legal
      commission, for the purpose of plundering other vessels on
      the high seas.

   3. One who infringes the law of copyright, or publishes the
      work of an author without permission.

   {Pirate perch} (Zo["o]l.), a fresh-water percoid fish of the
      United States ({Aphredoderus Sayanus}). It is of a dark
      olive color, speckled with blackish spots.

Pirate \Pi"rate\, v. i. [imp. & p. p. {Pirated}; p. pr. & vb. n.
   {Pirating}.] [Cf. F. pirater.]
   To play the pirate; to practice robbery on the high seas.

Pirate \Pi"rate\, v. t.
   To publish, as books or writings, without the permission of
   the author.

Source : WordNet®

pirate
     v 1: copy illegally; of published material
     2: take arbitrarily or by force; "The Cubans commandeered the
        plane and flew it to Miami" [syn: {commandeer}, {hijack},
        {highjack}]

pirate
     n 1: someone who uses another person's words or ideas as if they
          were his own [syn: {plagiarist}, {plagiarizer}, {plagiariser},
           {literary pirate}]
     2: someone who robs at sea or plunders the land from the sea
        without having a commission from any sovereign nation
        [syn: {buccaneer}, {sea robber}, {sea rover}]
     3: a ship manned by pirates [syn: {pirate ship}]

Source : Free On-Line Dictionary of Computing

pirate
     
        {software pirate}