holy day of obligation - a day when Catholics must attend Mass and refrain from servile work, and Episcopalians must take Communion

Christian religion, Christianity - a monotheistic system of beliefs and practices based on the Old Testament and the teachings of Jesus as embodied in the New Testament and emphasizing the role of Jesus as savior

church doctrine, religious doctrine, creed, gospel - the written body of teachings of a religious group that are generally accepted by that group