Source : Webster's Revised Unabridged Dictionary (1913)

Exitial \Ex*i"tial\, Exitious \Ex*i"tious\, a. [L. exitialis,
   exitious, fr. exitium a going out, a going to naught, i. e.,
   ruin, fr. exire to go out: cf. F. exitial.]
   Destructive; fatal. [Obs.] ``Exitial fevers.'' --Harvey.