Source : Webster's Revised Unabridged Dictionary (1913)

Jetty \Jet"ty\, n.; pl. {Jetties}. [F. jet['e]e a pier, a jetty,
   a causeway. See {Jet} a shooting forth, and cf. {Jutty}.]
   1. (Arch.) A part of a building that jets or projects beyond
      the rest, and overhangs the wall below.

   2. A wharf or pier extending from the shore.

   3. (Hydraul. Engin.) A structure of wood or stone extended
      into the sea to influence the current or tide, or to
      protect a harbor; a mole; as, the Eads system of jetties
      at the mouth of the Mississippi River.

   {Jetty ad} (Naut.), a projecting part at the end of a wharf;
      the front of a wharf whose side forms one of the cheeks of
      a dock.