Mid 16th century; earliest use found in Christopher Langton (1521–1578), physician. From classical Latin exitiōsus causing death or destruction, deadly from exitium + -ōsus.
Definition of exitious in US English:
exitious
adjective
rare
= exitial.
Origin
Mid 16th century; earliest use found in Christopher Langton (1521–1578), physician. From classical Latin exitiōsus causing death or destruction, deadly from exitium + -ōsus.