Entry 3 senses · 2 variants Webster, 1913 Postillate · Pos·til·late · IPA v. t. v. i. 01 v. t. To explain by marginal notes; to postil. 1. To explain by marginal notes; to postil. “Tracts . . . postillated by his own hand.” — C. Knight. 02 v. i. To write postils; to comment. 1. To write postils; to comment. 2. To preach by expounding Scripture verse by verse, in regular order.