earnest

Synonyms: ardent busy devoted diligent eager fervent fervid heartfelt impassioned industrious keen passionate perseverant purposeful sedulous sincere urgent vehement warm wholehearted zealous

Antonyms: flippant unconcerned unenthusiastic unpassionate unpurposeful unthoughtful

Synonyms: close constant determined firm fixed for real grave intent mean business meaningful no-fooling no-nonsense playing hard ball resolute resolved sedate sincere sober solemn somber stable staid steady thoughtful weighty

Antonyms: flippant insincere thoughtless trivial unimportant unserious