Simply stated, a provost is the Chief Academic Officer of a College or University. The word provost dates back to the 10th century.
From Random House Dictionary of the English Language, Second Edition:
Excerpts from the Oxford English Dictionary, Second Edition, 1989:
...One set or placed over others; a superintendent, president, head, chief; used generally as an equivalent of the uses of præpositus in ancient and medieval Latin, and of the descended terms in French and other languages, and spec. as the proper title of certain ecclesiastical and secular officers in England and Scotland, or as a rendering of French prevost, prévôt, formerly used to designate various officials...
In earlier instances, a survival from the ecclesiastical establishments in which these originated; in later instances an extension of the name to subsequent foundations. The title is borne by the heads of Oriel, Queen's, and Worcester Colleges at Oxford, King's College, Cambridge, and Trinity College, Dublin; also of Eton College, and now or formerly of certain other colleges in England, Scotland, the United States, etc.
Also....Applied to the archangel Michael as leader of the heavenly host.....
1413 Pilgr. Sowle (Caxton) i. ii. (1859) 3, I wil bringe hym bifore Mychael the prouost of heuene.
1521 in Market Harb. Records (1890) 216 The holy Archangell Mychell, the provest off paradyse.