1.AdjectiveEssential or decisive for determining the outcome or future of something; extremely important; vital.
"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.AdjectiveCruciform or cruciate; cross-shaped.
3.AdjectiveVery good; excellent; particularly applied to reggae music.
"Delbert Wilkins is the most crucial pirate radio DJ in Brixton."