MIRTHLESS Meaning of MIRTHLESS in English adj. 25B6; adjective HUMOURLESS, unamused, grim, sour, surly, dour, sullen, sulky, gloomy, mournful, melancholy, doleful, miserable, grumpy. cheerful. Concise Oxford thesaurus English vocabulary. Краткий оксфордский словарь английского языка тезаурус. 2012