2. fully attended (of a congregation of a council, church, etc.)
► uses
Uses:
In fact, many of the Constitution’s clauses specially accommodated or actually strengthened slavery, although the word itself appeared nowhere in the document. Article I temporarily barred Congress from using its otherwise plenary power over immigration and international trade to end the importation of African and Caribbean slaves.
Akhil Reed Amar. America's Constitution: A Biography (2005)
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The clerk several times used the word “plenary” (of the service), a word Petya did not understand.