[1] : WordNet (r) 2.0

hack on
     v : fix a computer program piecemeal until it works; "i'm not
         very good at hacking but i'll give it my best" syn: hack
see also:
hack 

[2] : Jargon File (4.3.1, 29 Jun 2001)

hack on vt. very common to hack; implies that the subject is some
   pre-existing hunk of code that one is evolving, as opposed to something
   one might hack up.


see also:
hack hack up 

[3] : The Free On-line Dictionary of Computing (27 SEP 03)

hack on
     
        to hack; implies that the subject is some pre-existing hunk
        of code that one is evolving, as opposed to something one
        might hack up.
     
        jargon file
     
     
see also:
hack hack up jargon file 

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Hack, definition of term: Hack
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