A small European plum (Prunus communis, var. insitita). See Plum.

A small tree or large shrub bearing black fruits 1-1.5in. long with comparatively large stones. Spreads by cuckers - shoots arising from underground from parts of the root system - and therefore often develops into dense stands. Frequently found near to former habitation; not much grown today. Technically a sub species of the plum and its allies; the normal plum of gardens is another sub species. (Beresford, Maurice and Hurst, John. Wharram Percy: Deserted Medieval Village, 136)

a purple wild plum.

The bully tree.