The Collaborative International Dictionary of English v.0.48:

Cinque Ports \Cinque" Ports`\ [Cinque + port.] (Eng. Hist.)
   Five English ports, to which peculiar privileges were
   anciently accorded; -- viz., Hastings, Romney, Hythe, Dover,
   and Sandwich; afterwards increased by the addition of
   Winchelsea, Rye, and some minor places.
   [1913 Webster]

   Baron of the Cinque Ports. See under Baron.
      [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

CINQUE PORTS, Eng. law. Literally, five ports. The name by which the five
ports of Hastings, Ramenhale, Hetha or Hethe, Dover, and Sandwich, are
known. 2. These ports have peculiar charges and services imposed upon them,
and were entitled to certain privileges and liberties. See Harg. L. Tr. 106-
113.