Source : Webster's Revised Unabridged Dictionary (1913)

Sloe \Sloe\, n. [OE. slo, AS. sl[=a]; akin to D. slee, G.
   schlehe, OHG. sl$ha, Dan. slaaen, Sw. sl?n, perhaps
   originally, that which blunts the teeth, or sets them on edge
   (cf. {Slow}); cf. Lith. sliwa a plum, Russ. sliva.] (Bot.)
   A small, bitter, wild European plum, the fruit of the
   blackthorn ({Prunus spinosa}); also, the tree itself.

Source : WordNet®

sloe
     n 1: wild plum of northeastern United States having dark purple
          fruits with yellow flesh [syn: {Allegheny plum}, {Alleghany
          plum}, {Prunus alleghaniensis}]
     2: a thorny Eurasian bush with plumlike fruits [syn: {blackthorn},
         {Prunus spinosa}]
     3: small sour dark purple fruit of especially the Allegheny
        plum bush