From The Collaborative International Dictionary of English v.0.48:
Rector \Rec"tor\ (r?k"t?r), n. [L., fr. regere, rectum, to lead
straight, to rule: cf. F. recteur. See Regiment, Right.]
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1. A ruler or governor. [R.]
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God is the supreme rector of the world. --Sir M.
Hale.
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2.
(a) (Ch. of Eng.) A clergyman who has the charge and cure
of a parish, and has the tithes, etc.; the clergyman
of a parish where the tithes are not impropriate. See
the Note under Vicar. --Blackstone.
(b) (Prot. Epis. Ch.) A clergyman in charge of a parish.
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3. The head master of a public school. [Scot.]
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4. The chief elective officer of some universities, as in
France and Scotland; sometimes, the head of a college; as,
the Rector of Exeter College, or of Lincoln College, at
Oxford.
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5. (R. C. Ch.) The superior officer or chief of a convent or
religious house; and among the Jesuits the superior of a
house that is a seminary or college.
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