D defs.my
Entry 1 sense Webster, 1913

A cappella

/ə käp-ĕl'-ə/ · A cap·pel·la · IPA /ˌɑ kəˈpɛl.ə/
01 In church or chapel style; -- said of compositions sung in the old church style, without instrumental accompaniment; as, a mass a capella, …
  1. 1.
    In church or chapel style; -- said of compositions sung in the old church style, without instrumental accompaniment; as, a mass a capella, i. e., a mass purely vocal.(Mus.)