Webster's Revised Unabridged Dictionary · 1913

Septic

Septic , adjective

[Septi- + -ic.]

(Mathematics) Of the seventh degree or order.
(Mathematics) A quantic of the seventh degree.

Septic , adjective

[Latin septicus, Greek {not transcribed}, from {not transcribed} to make putrid: compare French septique.]

Having power to promote putrefaction.

Also: Septical

Septic , noun

A substance that promotes putrefaction.