What is the Latin word for undutiful?

The usual Latin words for “undutiful” are impius, inofficiōsus. The right choice depends on the sense; see the distinctions below.

English → Latin

“undutiful” in Latin

impiusdisloyal, undutiful; godless, impious, unpatriotic; damned, accursed inofficiōsusnull and void

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

undutiful

impius (wickedly violating the pietas that should be observed toward parents, etc.; impius erga parentes, Suet.): inofficiosus (neglecting to perform kind offices, etc., in aliquem, Cic.). Vid: DISOBEDIENT.

Quick answer

What is the Latin word for undutiful?: The usual Latin words for “undutiful” are impius, inofficiōsus. 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.