'Spar buoy' definitions:

Definition of 'spar buoy'

noun

A buoy resembling a vertical log

From: GCIDE

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. [1913 Webster]
2. (Arch.) Formerly, a piece of timber, in a general sense; -- still applied locally to rafters. [1913 Webster]
3. The bar of a gate or door. [Obs.] --Chaucer. [1913 Webster]
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. [1913 Webster]