Definition of unmirthfully in English:

unmirthfully

Pronunciation /(ˌ)ʌnˈməːθfʊli/ /(ˌ)ʌnˈməːθf(ə)li/

adverb

  • Mirthlessly; without humour.

Origin

Late 19th century; earliest use found in Allen's Indian Mail. From un- + mirthfully.