<p><strong>Noun</strong></p><ul><li>the small, sour, blackish fruit of the blackthorn, <em>Prunus spinosa</em>, of the rose family.</li><li>the shrub itself.</li><li>any of various other plants of the genus <em>Prunus</em>, as a shrub or small tree, <em>P. alleghaniensis</em>, bearing dark-purple fruit.</li></ul>