1) A tyrant.
2) A lying, cheating, or sneaky person.
3) A dislikeable person.
4) A total and utter bastard.
Also a proper noun.
1) The name of a ruthless tyrant who made grand promises to his people which turned out to be a bunch of stupid lies. Several spoke out against him, but they were quickly silenced. The masses were like sheep at his feet, until he was overthrown by the goodly and noble Suzaku.
Man, shut up! You are such an Omnitor!
What were you doin? Were you spying on me, you Omnitor?!