Definition of: serious

(sir′ē·əs) adjective
1. Grave and earnest in quality, feeling, or disposition; thoughtful; sober.
2. Said, planned, or done with full practical intent; not jesting or making a false pretense; being or done in earnest.
3. Of grave importance; weighty; attended with considerable danger or loss: a serious matter, a serious accident.
4. Particularly attentive to religion. [<MF sérieux <LL seriosus <L serius]
—se′ri·ous·ly adverb
—se′ri·ous·ness noun Synonyms: dangerous, demure, earnest, grave, great, important, momentous, sedate, sober, solemn. A serious person is sedate, sober, solemn; a serious purpose is earnest; a serious illness is dangerous; a serious business is important, and may be momentous. See BAD, GOOD, IMPORTANT, SEDATE. Antonyms: careless, gay, insignificant, jocose, jolly, light, slight, thoughtless, trifling, trivial, volatile.