What is the Latin word for unmerciful?

The usual Latin words for “unmerciful” are immisericors, dūrus, ferreus; also inhūmānus. The right choice depends on the sense; see the distinctions below.

English → Latin

“unmerciful” in Latin

immisericorspitiless, merciless dūrushard; rough; harsh; hardy; vigorous ferreusiron, made of iron; like or pertaining to iron; hard, cruel inhūmānusinhuman; savage, barbarous; uncivil, unmannerly, churlish, discourteous

Riddle & Arnold A Copious and Critical English–Latin Lexicon, 1864

unmerciful

immisericors (without compassion): durus (hard): ferreus (without feeling, iron-hearted): inhumanus (inhuman).

Quick answer

What is the Latin word for unmerciful?: The usual Latin words for “unmerciful” are immisericors, dūrus, ferreus; also inhūmānus. The right choice depends on the sense; see the distinctions below.

Entry from J. E. Riddle & T. K. Arnold, A Copious and Critical English–Latin Lexicon (rev. C. Anthon, New York: Harper, 1864), digitised by Fergus J. P. Walsh, CC BY-SA 4.0; Latin markup adapted by latindictionary.co.