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

page out
 vi.

    [MIT]

    1. To become unaware of one's surroundings temporarily, due to daydreaming
    or preoccupation. ?Can you repeat that? I paged out for a minute.? See 
    page in. Compare glitch, thinko.

    2. Syn. swap out; see swap.


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

page out

    What a paging system does when it
   copies part of a task's working memory from RAM to swap
   space on disk.

   [Jargon File]

   (1995-01-23)