(1):

(n.) A short homily or commentary on a passage of Scripture; as, the first postils were composed by order of Charlemagne.

(2):

(v. i.) To write postils, or marginal notes; to comment; to postillate.

(3):

(n.) Originally, an explanatory note in the margin of the Bible, so called because written after the text; hence, a marginal note; a comment.

(4):

(v. t.) To write marginal or explanatory notes on; to gloss.