A serious mistake that could cost someone his life is an example of a mistake that would be described as grievous.
- causing grief
- showing or characterized by grief: a grievous cry
- causing suffering; hard to bear; severe: grievous pain
- very serious; deplorable: a grievous fault
- atrocious; heinous: a grievous crime
Origin of grievousMiddle English grevous ; from Old French ; from grever: see grieve
- Causing grief, pain, or anguish: a grievous loss.
- Serious or dire; grave: a grievous crime.
Origin of grievousAnglo-Norman grevous, from grever, to harm, aggrieve, from Latin gravare, to burden; see grieve.
(comparative more grievous, superlative most grievous)