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

geek out
 vi.

    To temporarily enter techno-nerd mode while in a non-hackish context, for
    example at parties held near computer equipment. Especially used when you
    need to do or say something highly technical and don't have time to
    explain: ?Pardon me while I geek out for a moment.? See geek; see also 
    propeller head.


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

geek out

   To temporarily enter techno-nerd mode while in a non-hackish
   context, for example at parties held near computer equipment.
   Especially used when you need to do or say something highly
   technical and don't have time to explain: "Pardon me while I
   geek out for a moment."

   See computer geek, propeller head.

   [Jargon File]

   (1995-01-18)