Pronunciation: (blak'thôrn"),[key] —n. 1. a shrub or tree of the genus Crataegus, as C. calpodendron. 2. a walking stick made of a blackthorn tree or shrub.
3. Also called sloe. a much-branched, thorny, Old World shrub, Prunus spinosa, having white flowers and small plumlike fruits.
4. See pear haw.