z-carhttp://www.oed.com/dictionary/z-car_n%3Ftab%3Dmeaning_and_useZ-car, n.
First published 1986; not fully revised

Z-carnoun

  1. 1961–
    A police patrol car (after the title of a popular U.K. television series, from the radio call-sign ‘zulu’ allotted therein to a group of such cars); also used allusively.
    1. 1961
      The call-sign is ZULU—they call them Z-cars. There are two young constables in each, ready to deal with trouble.
      Radio Times 28 December 29/2
    2. 1963
      Z-car crashes.
      Daily Mail 23 April 1/6 (heading)
    3. 1965
      Two black Z-cars—powerful Humbers—keep driving around the half-mile circle every five minutes watching for strangers.
      Sunday Mail (Brisbane) 19 December 32/5
    4. 1976
      It's not like Barlow and Z Cars, all that shouting stuff and strong jaws. These boys, they was slimy.
      ‘D. Craig’, Faith, Hope & Death xviii. 127

Originally published as part of the entry for Z, n.

Z, n. was first published in 1921; not fully revised.