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

vgrep
 /vee'grep/, v.,n.

    Visual grep. The operation of finding patterns in a file optically rather
    than digitally (also called an optical grep). See grep; compare vdiff.


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

vgrep
optical grep

    /vee'grep/ (Or "optical grep") Visual grep.
   Finding patterns in a file by eye rather than digitally.

   Compare vdiff.

   [Jargon File]

   (1998-02-06)