WordWeb Online

1. Lacking honour or integrity; deserving dishonour
   "dishonourable in thought and deed"
   - dishonorable [US]
    
2. Deceptive or fraudulent; disposed to cheat or defraud or deceive
   - dishonest, dishonorable [US]

See also: ambidextrous, beguiling, bent [Brit], black, blackguardly, corrupt, crooked, debasing, deceitful, deceptive, degrading, disgraceful, dishonourableness [Brit, Cdn], disreputable, double-dealing, double-faced, double-tongued, duplicitous, fallacious, false, fraudulent, honorableness [US], honorificabilitudinitatibus, honourableness [Brit, Cdn], ignoble, ignominious, inglorious, insincere, Janus-faced, misleading, opprobrious, picaresque, rascally, roguish, scoundrelly, shabby, shameful, shoddy, thieving, thievish, two-faced, unjust, unprincipled, untrustworthy, untrusty, unworthy, yellow