important or essential to the resolving of a crisis; decisive
Talks are at a crucial stage
(often + to) of the greatest importance or significance
Your contribution is crucial to the operation
informal wonderful or excellent
crucially adv
French crucial from Latin cruc-, crux cross. Although crucial entered English in the early 18th cent. in the literal meaning ‘cross-shaped’, its modern senses did not appear until the 19th cent. They derived from Francis Bacon's Latin phrase instantia crucis ‘instance of the cross’ (i.e. a signpost at a fork in a road, where a decision has to be made), referring to an instance that settles the claims of two rival arguments