Noah Webster's New International Dictionary of the English Language

1. (n.) The act of illustrating; the act of making clear and distinct; education; also, the state of being illustrated, or of being made clear and distinct.

2. (n.) That which illustrates; a comparison or example intended to make clear or apprehensible, or to remove obscurity.

3. (n.) A picture designed to decorate a volume or elucidate a literary work.