In Roman law. A member of the aenatus. In old English law. A member of the royal council; a king’s councillor. In American law. One who is a member of a senate, either of the United States or of a state. Senatores sunt partes corporis regis. Senators are part of the body of the king. Staundef. 72, B.; 4 Inst 53, in marg.
SENATOR
TheLaw.com Law Dictionary & Black's Law Dictionary 2nd Ed.