The Collaborative International Dictionary of English v.0.48:

Cowberry \Cow"ber`ry\ (-b[e^]r`r[y^]), n.; pl. Cowberries
   (-r[i^]z). (Bot.)
   A species of Vaccinium (Vaccinium Vitis-id[ae]a), which
   bears acid red berries which are sometimes used in cookery;
   -- locally called mountain cranberry.
   [1913 Webster]