Source : Webster's Revised Unabridged Dictionary (1913)

Oar \Oar\, n [AS. [=a]r; akin to Icel. [=a]r, Dan. aare, Sw.
   [*a]ra; perh. akin to E. row, v. Cf. {Rowlock}.]
   1. An implement for impelling a boat, being a slender piece
      of timber, usually ash or spruce, with a grip or handle at
      one end and a broad blade at the other. The part which
      rests in the rowlock is called the loom.

   Note: An oar is a kind of long paddle, which swings about a
         kind of fulcrum, called a rowlock, fixed to the side of
         the boat.

   2. An oarsman; a rower; as, he is a good oar.

   3. (Zo["o]l.) An oarlike swimming organ of various
      invertebrates.

   {Oar cock}
      (Zo["o]l), the water rail. [Prov. Eng.]

   {Spoon oar}, an oar having the blade so curved as to afford a
      better hold upon the water in rowing.

   {To boat the oars}, to cease rowing, and lay the oars in the
      boat.

   {To feather the oars}. See under {Feather}., v. t.

   {To lie on the oars}, to cease pulling, raising the oars out
      of water, but not boating them; to cease from work of any
      kind; to be idle; to rest.

   {To muffle the oars}, to put something round that part which
      rests in the rowlock, to prevent noise in rowing.

   {To put in one's oar}, to give aid or advice; -- commonly
      used of a person who obtrudes aid or counsel not invited.
      

   {To ship the oars}, to place them in the rowlocks.

   {To toss the oars}, To peak the oars, to lift them from the
      rowlocks and hold them perpendicularly, the handle resting
      on the bottom of the boat.

   {To trail oars}, to allow them to trail in the water
      alongside of the boat.

   {To unship the oars}, to take them out of the rowlocks.

Oar \Oar\, v. t. & i. [imp. & p. p. {Oared}; p. pr. & vb. n.
   {Oaring}.]
   To row. ``Oared himself.'' --Shak.

         Oared with laboring arms.                --Pope.

Source : WordNet®

oar
     n : an implement used to propel or steer a boat