n A picture designed to decorate a volume or elucidate a literary work.
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.
n That which illustrates; a comparison or example intended to make clear or apprehensible, or to remove obscurity.
n A calculated prevision of insurance premiums and returns (life insurance)"an illustration [...] is a computer projection of future premiums, cash values and death benefits based on the current dividend scale (whole life) or current interest rates and current costs of insurance (universal life)." taken from http://www.evaluatelifeinsurance.org