Buckthorn \Buck"thorn`\, n. (Bot.) A genus (Rhamnus) of shrubs or trees. The shorter branches of some species terminate in long spines or thorns. See Rhamnus. [1913 Webster]

Sea buckthorn, a plant of the genus Hippopha["e]. [1913 Webster]

Source: The Collaborative International Dictionary of English v.0.48
 

Buckthorn \Buck"thorn`\, n. (Bot.) A genus (Rhamnus) of shrubs or trees. The shorter branches of some species terminate in long spines or thorns. See Rhamnus.

Sea buckthorn, a plant of the genus Hippopha["e].

Source: Webster's Revised Unabridged Dictionary (1913)