Emily Dickinson Lexicon

TY'RANT, n. [L. tyrannus; Gr. τυραννος. The Welsh has teyrn, a king or sovereign, which Owen says is compounded of te, (that spreads,) and gyrn, imperious, supreme, from gyr, a driving. The Gaelic has tiarna and tighearna, a lord, prince or ruler, from tigh, a house; indicating that the word originally signified the master of a family merely, or the head of a clan. There is some uncertainty as to the real origin of the word. It originally signified merely a chief, king or prince.]

1. A monarch or other ruler or master, who uses power to oppress his subjects; a person who exercises unlawful authority, or lawful authority in an unlawful manner; one who by taxation, injustice or cruel punishment, or the demand of unreasonable services, imposes burdens and hardships on these under his control, which law and humanity do not authorize, or which the purposes of government do not require.
2. A despotic ruler; a cruel master; an oppressor. Love, to a yielding heart is a king, to a resisting heart is a tyrant. Sidney.