Source : Webster's Revised Unabridged Dictionary (1913)

Port \Port\, n. [F. porte, L. porta, akin to portus; cf. AS.
   porte, fr. L. porta. See {Port} a harbor, and cf. {Porte}.]
   1. A passageway; an opening or entrance to an inclosed place;
      a gate; a door; a portal. [Archaic]

            Him I accuse The city ports by this hath entered.
                                                  --Shak.

            Form their ivory port the cherubim Forth issuing.
                                                  --Milton.

   2. (Naut.) An opening in the side of a vessel; an embrasure
      through which cannon may be discharged; a porthole; also,
      the shutters which close such an opening.

            Her ports being within sixteen inches of the water.
                                                  --Sir W.
                                                  Raleigh.

   3. (Mach.) A passageway in a machine, through which a fluid,
      as steam, water, etc., may pass, as from a valve to the
      interior of the cylinder of a steam engine; an opening in
      a valve seat, or valve face.

   {Air port}, {Bridle port}, etc. See under {Air}, {Bridle},
      etc.

   {Port bar} (Naut.), a bar to secure the ports of a ship in a
      gale.

   {Port lid} (Naut.), a lid or hanging for closing the
      portholes of a vessel.

   {Steam port}, & {Exhaust port} (Steam Engine), the ports of
      the cylinder communicating with the valve or valves, for
      the entrance or exit of the steam, respectively.

Exhaust \Ex*haust"\, a. [L. exhaustus, p. p.]
   1. Drained; exhausted; having expended or lost its energy.

   2. Pertaining to steam, air, gas, etc., that is released from
      the cylinder of an engine after having preformed its work.

   {Exhaust draught}, a forced draught produced by drawing air
      through a place, as through a furnace, instead of blowing
      it through.

   {Exhaust fan}, a fan blower so arranged as to produce an
      exhaust draught, or to draw air or gas out of a place, as
      out of a room in ventilating it.

   {Exhaust nozzle}, {Exhaust orifice} (Steam Engine), the blast
      orifice or nozzle.

   {Exhaust pipe} (Steam Engine), the pipe that conveys exhaust
      steam from the cylinder to the atmosphere or to the
      condenser.

   {Exhaust port} (Steam Engine), the opening, in the cylinder
      or valve, by which the exhaust steam escapes.

   {Exhaust purifier} (Milling), a machine for sorting grains,
      or purifying middlings by an exhaust draught. --Knight.

   {Exhaust steam} (Steam Engine), steam which is allowed to
      escape from the cylinder after having been employed to
      produce motion of the piston.

   {Exhaust valve} (Steam Engine), a valve that lets exhaust
      steam escape out of a cylinder.