Webster’s Revised Unabridged Dictionary · 1913
Septic
Sep′tic (sĕp′tĭk), a. [Septi- + -ic.] (Math.) Of the seventh degree or order. — n. (Alg.) A quantic of the seventh degree.
Sep′tic, Sep′tic·al, a. [L. septicus, Gr. σηπτικός, fr. σήπειν to make putrid: cf. F. septique.] Having power to promote putrefaction.
Sep′tic, n. A substance that promotes putrefaction.