1. Incapable of being mitigated
   "stern and unmitigable accusations"

See also: implacable

• auto racing
• auto tire
• auto-changer
• auto-da-fé
• auto-mechanic
• autoantibody
• autobahn
• autobiographer
• autobiographic
• autobiographical
• autobiography
• autobus
• autocatalysis
• autocatalytic
• autocephalous
• autochthon
• autochthonal
• autochthonic
• autochthonous
• autochthony
• autoclave
• autocoid
• autocracy
• autocrat
• autocratic