An approach that permits the computer to work on several programs instead of one is

Keeping several programs in memory so the processor switches among them is multiprogramming.

An online thesaurus is a word lookup tool, unrelated to running many programs.

Overlapped processing merely means overlapping input output with computing, a narrower idea.

An outline processor is software for organising text outlines.

Multiprogramming raises processor use by never letting it sit idle.

Add-on: giving each program a fixed turn in time slices is the related idea of time sharing.