crucial

adjective3

1. •
   important enough to decide how something ends or what its future will be

   • The battle of Tali-Ihantala in 1944 is one of the crucial moments in the history of Finland.
   • A secure supply of crude oil is crucial for any modern nation, let alone a superpower.
2. •
   (slang) Very good; excellent; particularly applied to reggae music.

   • Delbert Wilkins is the most crucial pirate radio DJ in Brixton.
3. •
   (no longer used) Cruciform or cruciate; cross-shaped.