(in Great Britain) the seal affixed to grants, documents, etc., that are to pass the great seal, and to documents of less importance that do not require the great seal.
Origin of privy seal
Middle English word dating back to 1250–1300
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for privy seal
(often capitals) (in Britain) a seal affixed to certain documents issued by royal authority: of less rank and importance than the great seal
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012