noun Roman Catholic Church.
a branch of a religious order whose members are lay people following the avocations of a secular life.
a member of a Third Order who follows its rule in the community under ordinary simple vows.
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British Dictionary definitions for third order
RC Church a religious society of laymen affiliated to one of the religious orders and following a mitigated form of religious rule
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