what is a thorn
Webster Dictionary(0.00 / 0 votes)Rate this definition: 1  Thorn(noun) a hard and sharp-pointed projection from a woody stem; usually, a branch so transformed; a spine. 2  Thorn(noun) any shrub or small tree which bears thorns; especially, any species of the genus Crataegus, as the hawthorn, whitethorn, cockspur thorn.