encyclical
Concise Oxford English Dictionary © 2008 Oxford University Press:
encyclical /ɛnˈsɪklɪk(ə)l, ɪn-, -ˈsʌɪk-/
▶noun a letter sent by the pope to all bishops of the Roman Catholic Church.
– origin C17: via late L. from Gk enkuklios ‘circular, general’.
'encyclical' also found in these Oxford entries:

