Synonyms for serious

modified

1. Involving danger

   grave, severe, pressing; see dangerous 1, 2.

2. Involving earnestness

   solemn, grave, earnest, sedate, sober; see also solemn 1.

serious implies absorption in deep thought or involvement in something really important as distinguished from something frivolous or merely amusing he takes a serious interest in the theater; grave implies the dignified weightiness of heavy responsibilities or cares a grave expression on his face; solemn suggests an impressive or awe-inspiring seriousness a solemn ceremony; sedate implies a dignified, quiet or composed, sometimes even prim seriousness a sedate clergyman; earnest suggests a seriousness of purpose marked by sincerity and enthusiasm an earnest desire to help; sober implies a seriousness marked by temperance, self-control, emotional balance, etc. a sober criticism