The Collaborative International Dictionary of English v.0.48:

Skua \Sku"a\, n. [Icel. sk?fr, sk?mr.] (Zool.)
   Any jager gull; especially, the Megalestris skua; -- called
   also boatswain.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Jager \Ja"ger\, n. [G. j[aum]ger a hunter, a sportsman. Cf.
   Yager.] [Written also jaeger.]
   1. (Mil.) A sharpshooter. See Yager.
      [1913 Webster]

   2. (Zool.) Any species of gull of the genus Stercorarius.
      Three species occur on the Atlantic coast. The jagers
      pursue other species of gulls and force them to disgorge
      their prey. The two middle tail feathers are usually
      decidedly longer than the rest. Called also boatswain,
      and marline-spike bird. The name is also applied to the
      skua, or Arctic gull (Megalestris skua).
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tropic \Trop"ic\, a.
   Of or pertaining to the tropics; tropical.
   [1913 Webster]

   Tropic bird (Zool.), any one of three species of oceanic
      belonging to the genus Phaethon, found chiefly in
      tropical seas. They are mostly white, and have two central
      tail feathers very long and slender. The yellow-billed
      tropic bird. Phaethon flavirostris (called also
      boatswain), is found on the Atlantic coast of America,
      and is common at the Bermudas, where it breeds.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Boatswain \Boat"swain\, n. [Boat + swain.]
   1. (Naut.) An officer who has charge of the boats, sails,
      rigging, colors, anchors, cables, cordage, etc., of a
      ship, and who also summons the crew, and performs other
      duties.
      [1913 Webster]

   2. (Zool.)
      (a) The jager gull.
      (b) The tropic bird.
          [1913 Webster]

   Boatswain's mate, an assistant of the boatswain. --Totten.
      [1913 Webster]

WordNet (r) 3.0 (2006):

boatswain
    n 1: a petty officer on a merchant ship who controls the work of
         other seamen [syn: boatswain, bos'n, bo's'n, bosun,
         bo'sun]

Moby Thesaurus II by Grady Ward, 1.0:

50 Moby Thesaurus words for "boatswain":
   Big Brother, OD, auditor, boss, captain, chief, chief engineer,
   chief mate, commander, comptroller, controller, deck officer,
   floor manager, floorman, floorwalker, foreman, gaffer, ganger,
   head, headman, inspector, master, mate, monitor, naval officer,
   navigating officer, navigator, noncommissioned officer, overman,
   overseer, patron, pipes, proctor, quartermaster, sailing master,
   second mate, shipmaster, sirdar, skipper, slave driver, straw boss,
   subforeman, super, superintendent, supervisor, surveyor,
   taskmaster, the Old Man, visitor, watch officer