1. (a.) Having the form of a cross; appertaining to a cross; cruciform; intersecting; as, crucial ligaments; a crucial incision.

2. (a.) Severe; trying or searching, as if bringing to the cross; decisive; as, a crucial test.

aboriginal acute basal basic central charged clamorous climacteric compelling critical crying deciding decisive desperate dire elemental elementary embryonic emergent essential exigent fundamental generative genetic germinal high-pressure high-priority imperative imperious important in embryo in ovo insistent instant kairotic loaded major momentous necessary original pivotal pregnant pressing primal primary primeval primitive primordial pristine protogenic radical rudimentary seminal urgent vital