A person eligible to vote in an election; a member of an electorate, a voter.
A member of an electoral college; specifically (US) an official selected by a state as a member of the Electoral College to elect the president and vice president of the United States.
A person eligible to vote to elect a Member of Parliament.
Son or grandson of a czar (emperor) of the Russian Empire. (A more literal translation of the Russian would be grand prince.)
Ruler or monarch of a grand duchy.