flippant Antonyms

serious according to the book sober sincere severe set reverent respectful grave fixed feller ethic epochal solemn somber by the numbers bien pensant bog-standard archconservative buttoned-down button-down brassbound canonical authorised widespread weighty thoughtful earnest doctrinal derivative benevolent average authorized authoritative approved anaerobic adopted admitted acquired acknowledged accustomed acceptable broad broody courteous commutual commonplace common committed collective