The Free On-line Dictionary of Computing (30 December 2018):

RG58
thin Ethernet cable

    A common, low-impedance (52 ohm),
   quarter-inch diameter coaxial cable with BNC connectors,
   used for 10base2 Ethernet wiring, sometimes called
   "cheapernet" in comparison with "full spec" RG8 cabling.
   A member of the "Radio Guide" series.

   (2002-06-17)