(Science: botany) A small, bitter, wild European plum, the fruit of the blackthorn (prunus spinosa); also, the tree itself.
Origin: OE. Slo, AS. Sla; akin to D. Slee, G. Schlehe, OHG. Sl$ha, Dan. Slaaen, Sw. Sln, perhaps originally, that which blunts the teeth, or sets them on edge (cf. Slow); cf. Lith. Sliwa a plum, Russ. Sliva.