The Collaborative International Dictionary of English v.0.48:

Skulk \Skulk\, Skulker \Skulk"er\, n.
   One who, or that which, skulks.
   [1913 Webster]

WordNet (r) 3.0 (2006):

skulker
    n 1: someone shirking their duty by feigning illness or
         incapacity [syn: malingerer, skulker, shammer]
    2: someone waiting in concealment [syn: lurker, skulker,
       lurcher]

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

skulker
 n.

    Syn. prowler.


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

prowler
skulker

   (Unix) A daemon that is run periodically (typically once a
   week) to seek out and erase core files, truncate
   administrative logfiles, nuke "lost+found" directories, and
   otherwise clean up the cruft that tends to pile up in the
   corners of a file system.

   See also GFR, reaper, skulker.

   (1995-02-14)