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

run time

   1. The elapsed time to perform a computation on a particular
   computer.

   2. The amount of time a processor actually spent on a
   particular process and not on other processes or overhead (see
   time-sharing).

   3. The period of time during which a program is being
   executed, as opposed to compile-time or load time.  The term
   should be hyphenated when used as an adjective.

   4. run-time support.

   (2001-09-14)