al·la breve /ˌæləˈbrɛv, ˌɑləˈbrɛ(ˌ)ve/
  Al·la bre·ve  Old Church Music With one breve, or four minims, to measure, and sung faster like four crotchets; in quick common time; -- indicated in the time signature by ░.
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  alla breve
       n : a musical time signature indicating two or four half notes
           to a measure