WordWeb Online

1. Of extreme importance; vital to the resolution of a crisis
   "a crucial moment in his career";
   - important
    
2. Having essential relevance
   "crucial to the case"
    
3. Of the greatest importance
   "crucial information";
   - all-important, all important, essential, of the essence

See also: climacteric, critical, decisive, essential, important, life-and-death, life-or-death, material, of import, pivotal, polar

Antonym: noncrucial

Encyclopedia: Crucial