Source : Webster's Revised Unabridged Dictionary (1913)

Drastic \Dras"tic\, a. [Gr. ?, fr. ? to do, act: cf. F.
   drastique. See {Drama}.] (Med.)
   Acting rapidly and violently; efficacious; powerful; --
   opposed to {bland}; as, drastic purgatives. -- n. (Med.) A
   violent purgative. See {Cathartic}.

Source : WordNet®

drastic
     adj : forceful and extreme and rigorous; "drastic measures"