‖n.; pl.Opera [ L. See Opera. ] A work; specif. (Mus.), a musical composition. [ 1913 Webster ]
☞ Each composition, or set of pieces, as the composer may choose, is called an opus, and they are numbered in the order of their issue. (Often abbrev. to op.) [ 1913 Webster ]
Opus incertum. [ L. ] (Arch.) See under Incertum. [ 1913 Webster ]