资料来源 : Webster's Revised Unabridged Dictionary (1913)

Prophylactic \Proph`y*lac"tic\, Prophylactical
\Proph`y*lac"tic*al\, a. [Gr. ?, fr. ? to guard against; ?
   before + ? to guard: cf. F. prophylactique.] (Med.)
   Defending or preserving from disease; preventive. --Coxe.