Source : Webster's Revised Unabridged Dictionary (1913)

Tyrannize \Tyr"an*nize\, v. t.
   To subject to arbitrary, oppressive, or tyrannical treatment;
   to oppress.

Tyrannize \Tyr"an*nize\, v. i. [imp. & p. p. {Tyrannized}; p.
   pr. & vb. n. {Tyrannizing}.] [Cf. F. tyranniser, Gr. ? to
   take the part of tyrants.]
   To act the tyrant; to exercise arbitrary power; to rule with
   unjust and oppressive severity; to exercise power others not
   permitted by law or required by justice, or with a severity
   not necessary to the ends of justice and government; as, a
   prince will often tyrannize over his subjects; masters
   sometimes tyrannize over their servants or apprentices.

Source : WordNet®

tyrannize
     v 1: rule a country as a tyrant [syn: {tyrannise}, {grind down}]
     2: rule or exercise power over (somebody) in a cruel and
        autocratic manner; "her husband and mother-in-law
        tyrannize her" [syn: {tyrannise}, {domineer}]