(Or "wall clock time") 1. "Real world" time (what the clock on the wall shows), as opposed to the system clock's idea of time. 2. The real running time of a program, as opposed to the number of ticks required to execute it (on a time-sharing system these always differ, as no one program gets all the ticks, and on multiprocessor systems with good thread support one may get more processor time than real time).