Webster’s Revised Unabridged Dictionary · 1913
Prophylactic
Proph′y·lac′tic (prŏf′ĭ·lăk′tĭk or prō′fĭ·), n. [Cf. F. prophylactique.] (Med.) A medicine which preserves or defends against disease; a preventive.
Proph′y·lac′tic, Proph′y·lac′tic·al, a. [Gr. προφυλακτικός, fr. προφυλάσσειν to guard against; πρό before + φυλάσσειν to guard: cf. F. prophylactique.] (Med.) Defending or preserving from disease; preventive. Coxe.