2 definitions found From WordNet (r) 2.0 [wn]: blackthorn noun 1: a thorny Eurasian bush with plumlike fruits [syn: {sloe}, {Prunus spinosa}] 2: erect and almost thornless American hawthorn with somewhat pear-shaped berries [syn: {pear haw}, {pear hawthorn}, {Crataegus calpodendron}, {Crataegus tomentosa}] From The Collaborative International Dictionary of English v.0.44 [gcide]: Blackthorn \Black"thorn'\, noun (Bot.) (a) A spreading thorny shrub or small tree ({Prunus spinosa}), with blackish bark, and bearing little black plums, which are called sloes; the sloe. (b) A species of {Crat[ae]gus} or hawthorn ({Crat[ae]gus tomentosa}). Both are used for hedges.

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