1 the cruel and arbitrary use of authority.
2 a tyrannical act; tyrannical behaviour.
3 a rule by a tyrant. b a period of this. c a State ruled by a tyrant.
Derivatives:
tyrannous adj. tyrannously adv.
Etymology: ME f. OF tyrannie f. med.L tyrannia f. Gk turannia (as TYRANT)
Useful english dictionary. 2012.