Definition of phylaxis in US English:

phylaxis

noun

Biology
rare
  • The immunological protection of the body against infection. rare.

Origin

Early 20th century. From ancient Greek ϕύλαξις watching, guarding, a security from ϕυλακ-, stem of ϕυλάσσειν to guard + -σις, after French phylaxie.

Pronunciation

phylaxis

/fʌɪˈlaksɪs/