Blackthorn \Black"thorn`\, n. (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 ({C.
tomentosa}). Both are used for hedges.