The Collaborative International Dictionary of English v.0.48:

groundberry \groundberry\ n.
   A small prostrate or ascending shrub (Astroloma humifusum)
   having scarlet flowers and thin-fleshed succulent fruit
   resembling cranberries; sometimes placed in the genus
   Styphelia.

   Syn: native cranberry, cranberry heath, Astroloma
        humifusum, Styphelia humifusum.
        [WordNet 1.5]

   2. A creeping shrub of eastern North America (Gaultheria
      procumbens) having white bell-shaped flowers followed by
      spicy red berrylike fruit and shiny aromatic leaves that
      yield wintergreen oil.

   Syn: teaberry, wintergreen, checkerberry, mountain tea,
        creeping wintergreen, Gaultheria procumbens.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

ground-berry
    n 1: small prostrate or ascending shrub having scarlet flowers
         and succulent fruit resembling cranberries; sometimes
         placed in genus Styphelia [syn: native cranberry,
         groundberry, ground-berry, cranberry heath,
         Astroloma humifusum, Styphelia humifusum]
    2: creeping shrub of eastern North America having white bell-
       shaped flowers followed by spicy red berrylike fruit and
       shiny aromatic leaves that yield wintergreen oil [syn:
       teaberry, wintergreen, checkerberry, mountain tea,
       groundberry, ground-berry, creeping wintergreen,
       Gaultheria procumbens]