Webster's Revised Unabridged Dictionary · 1913

Blackthorn

Blackthorn ({not transcribed}) , noun

(a)
(Botany) A spreading thorny shrub or small tree (Prunus spinosa), with blackish bark, and bearing little black plums, which are called sloes; the sloe.
(b)
(Botany) A species of Cratagus or hawthorn (Cratagus tomentosa). Both are used for hedges.