The Collaborative International Dictionary of English v.0.48:
Tyrannize \Tyr"an*nize\ (t[i^]r"an*n[imac]z), v. i. [imp. & p.
p. Tyrannized (t[i^]r"an*n[imac]zd); p. pr. & vb. n.
Tyrannizing (t[i^]r"an*n[imac]`z[i^]ng).] [Cf. F.
tyranniser, Gr. tyranni`zein to take the part of tyrants.]
To act the tyrant; to exercise arbitrary power; to rule with
unjust and oppressive severity; to exercise power over 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.