Source : Webster's Revised Unabridged Dictionary (1913)

Tyrannic \Ty*ran"nic\ (?; 277), Tyrannical \Ty*ran"nic*al\, a.
   [L. tyrannicus, Gr. ?: cf. F. tyrannique. See {Tyrant}.]
   Of or pertaining to a tyrant; suiting a tyrant; unjustly
   severe in government; absolute; imperious; despotic; cruel;
   arbitrary; as, a tyrannical prince; a tyrannical master;
   tyrannical government. ``A power tyrannical.'' --Shak.

         Our sects a more tyrannic power assume.  --Roscommon.

         The oppressor ruled tyrannic where he durst. --Pope.
   -- {Ty*ran"nic*al*ly}, adv. -- {Ty*ran"nic*al*ness}, .

Source : WordNet®

tyrannical
     adj 1: of or relating to or associated with or resembling a
            dictatorship; "tyrannical suppression of liberty"
            [syn: {tyrannic}]
     2: marked by unjust severity or arbitrary behavior; "the
        oppressive government"; "oppressive laws"; "a tyrannical
        parent"; "tyrannous disregard of human rights" [syn: {oppressive},
         {tyrannous}]
     3: characteristic of an absolute ruler or absolute rule; having
        absolute sovereignty; "an authoritarian regime";
        "autocratic government"; "despotic rulers"; "a dictatorial
        rule that lasted for the duration of the war"; "a
        tyrannical government" [syn: {authoritarian}, {autocratic},
         {dictatorial}, {despotic}]