adjective
- unable to be mitigated; not to be mitigated.
adjective
- rare unable to be mitigated; relentless; unappeasable
1570s, from Latin immitigabilis, from assimilated form of in- “not” (see in- (1) + mitigabilis, from past participle stem of mitigare “make mild or gentle” (see mitigate). Related: Immitigably.