Webster's Revised Unabridged Dictionary · 1913

Cathartic

Cathartic , adjective

[Greek {not transcribed}, from {not transcribed} to cleanse, from {not transcribed} pure; akin to French chaste.]

1.
(Medicine) Cleansing the bowels; promoting evacuations by stool; purgative.
2.
Of or pertaining to the purgative principle of senna, as cathartic acid.

Also: Catharical

Cathartic , noun

[Greek {not transcribed}.]

(Medicine) A medicine that promotes alvine discharges; a purge; a purgative of moderate activity.

The cathartics are more energetic and certain in action that the laxatives, which simply increase the tendency to alvine evacuation; and less powerful and irritaint that the drastic purges, which cause profuse, repeated, and watery evacuations.