The Collaborative International Dictionary of English v.0.48:

jitney \jitney\ n.
   1. a small bus or similar vehicle carrying passengers on a
      fixed route, used for public transport. [WordNet sense 1]

   Note: Probably so called because they once charged a nickel
         for the ride. --RHUD
         [WordNet 1.5]

   2. A five-cent piece; a nickel. [slang, archaic]
      [PJC]

WordNet (r) 3.0 (2006):

jitney
    n 1: a vehicle carrying many passengers; used for public
         transport; "he always rode the bus to work" [syn: bus,
         autobus, coach, charabanc, double-decker, jitney,
         motorbus, motorcoach, omnibus, passenger vehicle]