background processing

(computer science) The execution of lower-priority programs when higher-priority programs are not being handled by a data-processing system. Computer processing that is not interactive or visible on the display screen.

Processing in which the program is not visibly interacting with the user. Earlier personal computers used operating systems that ran background tasks only when foreground tasks were idle, such as between keystrokes. Today's multitasking operating systems share time between background and foreground programs. Advanced operating systems on mainframes can prioritize each job.

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The noun has one meaning:

Meaning #1: the execution of low priority programs while higher priority programs are not using the processing system
  Synonym: backgrounding