The Collaborative International Dictionary of English v.0.48:

Spar \Spar\, n. [OE. sparre; akin to D. spar, G. sparren, OHG.
   sparro, Dan. & Sw. sparre, Icel. sparri; of uncertain origin.
   [root]171. Cf. Spar, v. t. ]
   1. (Naut.) A general term any round piece of timber used as a
      mast, yard, boom, or gaff.
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   2. (Arch.) Formerly, a piece of timber, in a general sense;
      -- still applied locally to rafters.
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   3. The bar of a gate or door. [Obs.] --Chaucer.
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   Spar buoy (Naut.), a buoy anchored by one end so that the
      other end rises above the surface of the water.

   Spar deck (Naut.), the upper deck of a vessel; especially,
      in a frigate, the deck which is continued in a straight
      line from the quarter-deck to the forecastle, and on which
      spare spars are usually placed. See under Deck.

   Spar torpedo (Naut.), a torpedo carried on the end of a
      spar usually projecting from the bow of a vessel, and
      intended to explode upon contact with an enemy's ships.
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WordNet (r) 3.0 (2006):

spar buoy
    n 1: a buoy resembling a vertical log