[ 'rəʊz(ə)ri ]
■ noun ( plural rosaries )
1》 (in the Roman Catholic Church) a form of devotion in which five (or fifteen) decades of Hail Marys are repeated, each decade preceded by an Our Father and followed by a Glory Be.
2》 a string of beads for keeping count in such a devotion or in the devotions of some other religions.
Origin
ME (in the sense 'rose garden'): from L. rosarium 'rose garden', based on rosa 'rose'.