Source : Webster's Revised Unabridged Dictionary (1913)

Gudgeon \Gud"geon\, n. [OE. gojon, F. goujon, from L. gobio, or
   gob, Gr. ? Cf. {1st Goby}. ]
   1. (Zo["o]l.) A small European freshwater fish ({Gobio
      fluviatilis}), allied to the carp. It is easily caught and
      often used for food and for bait. In America the
      killifishes or minnows are often called {gudgeons.}

   2. What may be got without skill or merit.

            Fish not, with this melancholy bait, For this fool
            gudgeon, this opinion.                --Shak.

   3. A person easily duped or cheated. --Swift.

   4. (Mach.) The pin of iron fastened in the end of a wooden
      shaft or axle, on which it turns; formerly, any journal,
      or pivot, or bearing, as the pintle and eye of a hinge,
      but esp. the end journal of a horizontal.

   6. (Naut.) A metal eye or socket attached to the sternpost to
      receive the pintle of the rudder.

   {Ball gudgeon}. See under {Ball}.