An encyclical is an official letter written by the Pope and sent to all Roman Catholic bishops, usually in orderto make a statement about the official teachings of the Church.
encyclical in British English
(ɛnˈsɪklɪkəl)
noun
1.
a letter sent by the pope to all Roman Catholic bishops throughout the world
adjective also: encyclic
2.
(of letters) intended for general or wide circulation
Word origin
C17: from Late Latin encyclicus, from Greek enkuklios general, from kuklos circle