adjective somber, humorless
Synonyms: austere, bound, bound and determined, businesslike, cold sober, contemplative, deadpan, deliberate, determined, downbeat, earnest, funereal, genuine, go for broke, grave, grim, honest, intent, long-faced, meditative, no-nonsense, pensive, pokerfaced, reflective, resolute, resolved, sedate, set, severe, sincere, sober, solemn, staid, steady, stern, thoughtful, unhumorous, unsmiling, weighty
Antonyms: flippant, funny, happy, light
adjective crucial, weighty
Synonyms: arduous, dangerous, deep, difficult, far-reaching, fateful, fell, formidable, grave, grievous, grim, hard, heavy, important, laborious, major, meaning business, meaningful, menacing, momentous, no joke, no laughing matter, of consequence, operose, out for blood, playing hard ball, pressing, severe, significant, smoking, sobering, strenuous, strictly business, threatening, tough, ugly, unamusing, unhumorous, urgent, worrying
Antonyms: light, minor, trivial, unimportant, unserious