Source : Webster's Revised Unabridged Dictionary (1913)

Breve \Breve\ (br[=e]v), n. [It. & (in sense 2) LL. breve, fr.
   L. brevis short. See {Brief}.]
   1. (Mus.) A note or character of time, equivalent to two
      semibreves or four minims. When dotted, it is equal to
      three semibreves. It was formerly of a square figure (as
      thus: ? ), but is now made oval, with a line perpendicular
      to the staff on each of its sides; -- formerly much used
      for choir service. --Moore.

   2. (Law) Any writ or precept under seal, issued out of any
      court.

   3. (Print.) A curved mark [[breve]] used commonly to indicate
      the short quantity of a vowel.

   4. (Zo["o]l.) The great ant thrush of Sumatra ({Pitta
      gigas}), which has a very short tail.

Source : WordNet®

breve
     n : a diacritical mark (u-curved) placed over a vowel to
         indicate a short sound