The Collaborative International Dictionary
Bilberry \Bil"ber*ry\, n.; pl. Bilberries. [Cf. Dan. b["o]lleb[ae]r bilberry, where b["o]lle is perh. akin to E. ball.]
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(Bot.) The European whortleberry ( Vaccinium myrtillus); also, its edible bluish black fruit.
There pinch the maids as blue as bilberry.
--Shak. (Bot.) Any similar plant or its fruit; esp., in America, the species Vaccinium myrtilloides, Vaccinium c[ae]spitosum and Vaccinium uliginosum.
Wikipedia
Vaccinium myrtilloides is a shrub with common names including common blueberry, velvetleaf huckleberry, velvetleaf blueberry, Canadian blueberry, and sourtop blueberry. It is common in much of North America, reported from all 10 Canadian province plus Nunavut and Northwest Territories, as well as from the northeastern and Great Lakes states in the United States. It is also known to occur in Montana and Washington.