From pivot +‎ -al.

• IPA^(key): /ˈpɪvətəl/

• Audio (US):

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pivotal (comparative more pivotal, superlative most pivotal)

1. Of, relating to, or being a pivot.
2. Being of crucial importance; central, key.
   • 2013 June 7, Joseph Stiglitz, “Globalisation is about taxes too”, in The Guardian Weekly, volume 188, number 26, page 19:

     It is time the international community faced the reality: we have an unmanageable, unfair, distortionary global tax regime. It is a tax system that is pivotal in creating the increasing inequality that marks most advanced countries today […].

   • 2021 January 13, “Packham initiates new petition opposing HS2”, in RAIL, issue 922, page 12:

     "Crucially, HS2 is already playing a pivotal role in helping Britain's post-pandemic economic recovery.

pivotal m or f (plural pivotais)

1. pivotal; crucial (being the most important)

   Synonym: crucial