Source : Free On-Line Dictionary of Computing

wall time
     
        (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 {tick}s 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).
     
        [{Jargon File}]