alla breve(n = noun.communication) - a musical time signature indicating two or four half notes to a measure;
is a kind of musical time signature, time signature
With one breve, or four minims, to measure, and sung faster like four crotchets; in quick common time; -- indicated in the time signature by 1913 Webster]
alla breve, n. Mus. a time signature indicating 2 or 4 minim beats in a bar.
Etymology:
It., = at the BREVE