WordNet (r) 3.0 (2006):

swap space
    n 1: the disk space that is set aside for virtual memory [syn:
         swap space, swap file]

The Jargon File (version 4.4.7, 29 Dec 2003):

swap space
 n.

    Storage space, especially temporary storage space used during a move or
    reconfiguration. ?I'm just using that corner of the machine room for swap
    space.?


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

swap space

    An area of disk (e.g. a swap file) used
   to store the state of a process that has been swapped out.
   Under a virtual memory system, it is the amount of swap
   space rather than the amount of physical memory which
   determines the maximum size of a single process and the
   maximum total size of all active processes.

   [Jargon File]

   (1994-11-03)