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

10base2

    (Or "cheapernet") The variant of Ethernet that
   uses thin coaxial cable (RG-58 or similar), as opposed to
   10base5 cable.

   The "10" means 10 Mbps, "base" means "baseband" as opposed
   to radio frequency and "2" means a maximum single cable
   length of 200m.

   (1995-11-14)