The DICT Development Group

  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