Source : Webster's Revised Unabridged Dictionary (1913)

Felonious \Fe*lo"ni*ous\, a.
   Having the quality of felony; malignant; malicious;
   villainous; traitorous; perfidious; in a legal sense, done
   with intent to commit a crime; as, felonious homicide.

         O thievish Night, Why should'st thou, but for some
         felonious end, In thy dark lantern thus close up the
         stars?                                   --Milton.
   -- {Fe*lo"ni*ous*ly}, adv. -- {Fe*lo"ni*ous*ness}, n.

Source : WordNet®

felonious
     adj : involving or being or having the nature of a crime; "a
           criminal offense"; "criminal abuse"; "felonious intent"
           [syn: {criminal}]