Entry 1 sense Webster, 1913 Congregationalist · Con·gre·ga·tion·al·ist · IPA /kɑŋɡɹəˈɡeɪʃənəlɪst/ 01 n. One who belongs to a Congregational church or society; one who holds to Congregationalism. 1. One who belongs to a Congregational church or society; one who holds to Congregationalism.