(a.) Of or pertaining to a pivot or turning point; belonging to, or constituting, a pivot; of the nature of a pivot; as, the pivotal opportunity of a career; the pivotal position in a battle.

acute axial behind the scenes capital cardinal causal causative centermost central centralized centric centroidal centrosymmetric charged clamorous climacteric compelling concentrated constitutive critical crucial crying decisive determinative effectual emergent essential etiological exigent focal formative geocentric high-pressure high-priority imperative imperious important insistent instant institutive kairotic key loaded middle middlemost midmost momentous occasional omphalic originative overriding overruling pregnant pressing principal radical ruling significant umbilical urgent vital