FATAL Copy link • FATALfatalis (determined by fate; dependent on fate; and then fatally unfortunate, untoward): perniciosus (hurtful, ruinous). In a less strong sense, miser, infelix, luctuosus. By this fatal war, hoc misero fatalique bello. Causing death, mortifer. A fatal disease, gravis et mortifer morbus: to have a disorder that will prove fatal, gravi et mortifero morbo affectum esse; mortifero morbo correptum esse; mortifere aegrotare (Plaut.).