The Collaborative International Dictionary of English v.0.48:

Oxheart \Ox"heart`\, n.
   A large heart-shaped cherry, either black, red, or white.
   [1913 Webster]

WordNet (r) 3.0 (2006):

oxheart
    n 1: any of several cultivated sweet cherries having sweet juicy
         heart-shaped fruits [syn: heart cherry, oxheart,
         oxheart cherry]
    2: large heart-shaped sweet cherry with soft flesh [syn: heart
       cherry, oxheart, oxheart cherry]