I. noun 1. a member of an Augustinian order; specifically a friar of the Hermits of St. Augustine founded in 1256 and devoted to educational, missionary, and parish work 2. a follower of St. Augustine II. adjective 1. of or relating to St. Augustine or his doctrines 2. of or relating to any of several orders under a rule ascribed to St. Augustine • Augustinianism noun