Definition of per fas et nefas in US English:

per fas et nefas

(also per fas aut nefas)

adverb

  • By right or wrong; by fair or unfair means; by any means (good or bad).

Origin

Early 17th century; earliest use found in William Watson (?1559–1603), Roman Catholic priest and conspirator. From post-classical Latin per fas et nefas by right or wrong from classical Latin per + fās that which is right + et and + nefās offence against divine or moral law.

Pronunciation

per fas et nefas

/pəː ˌfɑːs ɛt ˈneɪfɑːs/