(1):

(v. t.) To render rational; to free from radical signs or quantities.

(2):

(v. i.) To use, and rely on, reason in forming a theory, belief, etc., especially in matters of religion: to accord with the principles of rationalism.

(3):

(v. t.) To interpret in the manner of a rationalist.

(4):

(v. t.) To make rational; also, to convert to rationalism.

(5):

(v. t.) To form a rational conception of.