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

power cycle
 vt.

    (also, cycle power or just cycle) To power off a machine and then power it
    on immediately, with the intention of clearing some kind of hung or 
    gronked state. See also Big Red Switch. Compare Vulcan nerve pinch, 
    bounce (sense 4), and boot, and see the Some AI Koans (in Appendix A)
    about Tom Knight and the novice.


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

power cycle

    (Or "cycle power", "cycle") To turn a machine's
   power off and on, with the intention of clearing some kind of
   hung or gronked state.  Synonym 120 reset; see also Big
   Red Switch.  Compare Vulcan nerve pinch, bounce and
   boot, and see the AI Koan about Tom Knight and the novice.

   [Jargon File]

   (2012-02-09)