The Collaborative International Dictionary of English v.0.48:

Abet \A*bet"\, v. t. [imp. & p. p. Abetted; p. pr. & vb. n.
   Abetting.] [OF. abeter; a (L. ad) + beter to bait (as a
   bear), fr. Icel. beita to set dogs on, to feed, originally,
   to cause to bite, fr. Icel. b[imac]ta to bite, hence to bait,
   to incite. See Bait, Bet.]
   1. To instigate or encourage by aid or countenance; -- used
      in a bad sense of persons and acts; as, to abet an
      ill-doer; to abet one in his wicked courses; to abet vice;
      to abet an insurrection. "The whole tribe abets the
      villany." --South.
      [1913 Webster]

            Would not the fool abet the stealth,
            Who rashly thus exposed his wealth?   --Gay.
      [1913 Webster]

   2. To support, uphold, or aid; to maintain; -- in a good
      sense. [Obs.].

            Our duty is urged, and our confidence abetted.
                                                  --Jer. Taylor.
      [1913 Webster]

   3. (Law) To contribute, as an assistant or instigator, to the
      commission of an offense.
      [1913 Webster]

   Syn: To incite; instigate; set on; egg on; foment; advocate;
        countenance; encourage; second; uphold; aid; assist;
        support; sustain; back; connive at.
        [1913 Webster]