Source : WordNet®

ad hoc
     adj 1: often improvised or impromptu; "an ad hoc committee meeting"
     2: for or concerned with one specific purpose; "a coordinated
        policy instead of ad hoc decisions"
     adv : for one specific case; "they were appointed ad hoc"

Source : Free On-Line Dictionary of Computing

ad hoc
     
        Contrived purely for the purpose in hand rather than planned
        carefully in advance.  E.g. "We didn't know what to do about
        the sausage rolls, so we set up an ad-hoc committee".
     
        (1995-03-25)