Webster's Revised Unabridged Dictionary · 1913

A priori

A priori ({not transcribed})

[Latin a (ab) + prior former.]

1.
(Logic) Characterizing that kind of reasoning which deduces consequences from definitions formed, or principles assumed, or which infers effects from causes previously known; deductive or deductively. The reverse of a posteriori.
3.
(Philosophy) Applied to knowledge and conceptions assumed, or presupposed, as prior to experience, in order to make experience rational or possible.
A priori, that is, from these necessities of the mind or forms of thinking, which, though first revealed to us by experience, must yet have preexisted in order to make experience possible. — Coleridge