/proh'feuh lak"sis, prof'euh-/ , n.
1. Med.
a. the preventing of disease.
b. the prevention of a specific disease, as by studying the biological behavior, transmission, etc., of its causative agent and applying a series of measures against it.
2. prophylactic treatment, as the cleaning of the teeth by a dentist or dental hygienist.
[ 1835-45; pro- PRO- 2 + phýlaxis a watching, guarding, equiv. to phylak- (base of phylássein to guard) + -sis -SIS ]