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The Collaborative International Dictionary
Prophylactical

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.

Wiktionary
prophylactical

a. prophylactic; preventative