dewberry

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of several trailing prickly shrubs of the genus Rubus of North America and Eurasia, having purple or black fruit resembling blackberries.
• noun The fruit of any of these plants.

from The Century Dictionary.

• noun In England, the popular name of the Rubus cæsius, a bramble which grows in woods, thickets, hedges, and the borders of fields; the fruit of this plant. The fruit is black, with a bluish dewy bloom, and of an agreeable acid taste.
• noun In the United States, the popular name of Rubus Canadensis, the low blackberry, a trailing plant which has a large sweet fruit; the fruit of this plant.

from the GNU version of the Collaborative International Dictionary of English.

• noun The fruit of certain species of bramble (Rubus); in England, the fruit of Rubus cæsius, which has a glaucous bloom; in America, that of Rubus canadensis and Rubus hispidus, species of low blackberries.
• noun The plant which bears the fruit.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Small brambles of the genus Rubus which have stems that trail along the ground.
• noun The purple to black berries of these plants.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun blackberry-like fruits of any of several trailing blackberry bushes
• noun any of several trailing blackberry brambles especially of North America