serious

serious
    adj 1: concerned with work or important matters rather than play
           or trivialities; "a serious student of history"; "a
           serious attempt to learn to ski"; "gave me a serious
           look"; "a serious young man"; "are you serious or
           joking?"; "Don't be so serious!" [ant: {frivolous}]
    2: of great consequence; "marriage is a serious matter"
    3: causing fear or anxiety by threatening great harm; "a
       dangerous operation"; "a grave situation"; "a grave illness";
       "grievous bodily harm"; "a serious wound"; "a serious turn of
       events"; "a severe case of pneumonia"; "a life-threatening
       disease" [syn: {dangerous}, {grave}, {grievous}, {serious},
       {severe}, {life-threatening}]
    4: appealing to the mind; "good music"; "a serious book" [syn:
       {good}, {serious}]
    5: completely lacking in playfulness [syn: {unplayful},
       {serious}, {sober}] [ant: {playful}]
    6: requiring effort or concentration; complex and not easy to
       answer or solve; "raised serious objections to the proposal";
       "the plan has a serious flaw"
    

Serious \Se"ri*ous\, a. [L. serius: cf. F. s['e]rieux, LL.
   seriosus.]
   1. Grave in manner or disposition; earnest; thoughtful;
      solemn; not light, gay, or volatile.
      [1913 Webster]

            He is always serious, yet there is about his manner
            a graceful ease.                      --Macaulay.
      [1913 Webster]

   2. Really intending what is said; being in earnest; not
      jesting or deceiving. --Beaconsfield.
      [1913 Webster]

   3. Important; weighty; not trifling; grave.
      [1913 Webster]

            The holy Scriptures bring to our ears the most
            serious things in the world.          --Young.
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   4. Hence, giving rise to apprehension; attended with danger;
      as, a serious injury.
      [1913 Webster]

   Syn: Grave; solemn; earnest; sedate; important; weighty. See
        {Grave}.
        [1913 Webster] -- {Se"ri*ous*ly}, adv. --
        {Se"ri*ous*ness}, n.
        [1913 Webster]
    

189 Moby Thesaurus words for "serious":
      abandoned, acute, afire, alarming, ardent, arduous, austere,
      awe-inspiring, bad, bound, bound and determined, burning,
      businesslike, cogitative, cognitive, committed, comprehensive,
      concentrating, concentrative, conceptive, conceptual,
      conceptualized, consequential, considerable, contemplating,
      contemplative, critical, crucial, dangerous, dangersome, decided,
      decisive, decorous, dedicated, deep, definite, deliberating,
      deliberative, demure, determined, devoted, devout, difficult,
      dignified, dour, earnest, elevated, excogitating, exhaustive,
      explosive, faithful, fatal, fateful, fell, fervent, fervid, fiery,
      flaming, formal, formidable, fraught with danger, frowning, full,
      genuine, grand, grave, great, grievous, grim, grim-faced,
      grim-visaged, hearty, heated, heavy, honest, hot, hot-blooded,
      humorless, ideative, impassioned, important, imposing, in earnest,
      inspiring, intense, intent, intent on, introspective, irresistible,
      jeopardous, laborious, life-and-death, life-or-death, lofty,
      long-faced, loyal, main, majestic, major, maximum, meditating,
      meditative, menacing, mental, mighty, moderate, momentous, moving,
      museful, musing, nasty, no joke, no laughing matter, no-nonsense,
      noble, noetic, obstinate, on fire, operose, parlous, passionate,
      pensive, perfervid, periculous, perilous, persevering, persistent,
      plenary, poker-faced, pondering, portentous, powerful, precarious,
      prehensive, pressing, purposeful, red-hot, reflecting, reflective,
      relentless, resolute, resolved, ruminant, ruminating, ruminative,
      sedate, serious-minded, severe, significant, sincere,
      single-minded, sober, sober-minded, sobersided, solemn, somber,
      speculative, spirited, staid, stately, steady, stern, stone-faced,
      straight-faced, straightforward, strenuous, strong, sublime,
      temperate, tenacious, thinking, thought, thoughtful, threatening,
      total, tough, ugly, unamusing, unfunny, unsmiling, urgent,
      vehement, vital, warm, weighty, white-hot, wholehearted, wistful,
      zealous