From Longman Dictionary of Contemporary EnglishGregorian chantGre·go·ri·an chant /ɡrɪˌɡɔːriən ˈtʃɑːnt $ -ˈtʃænt/ noun [countable, uncountable] APMa kind of church music for voices alone
Examples from the Corpus
Gregorian chant• When he was about half-way he paused and whistled loudly like a blackbird that was attempting a Gregorian chant.• Computer science is a bit like a Gregorian chant a one-line melody changing state within larger scale sections.• The music is as old as Gregorian chant and as fresh as a Disney soundtrack.• Some of the allure is a residue of the Gregorian chant mania of a few years ago.Origin Gregorian chant (1700-1800) Because it is said to have been introduced by Pope Gregory I 