n. 1 a stiff sharp-pointed projection on a plant. 2 a thorn-bearing shrub or tree. 3 the name of an Old English and Icelandic runic letter, = th. on thorns continuously uneasy esp. in fear of being detected. thorn-apple 1 a poisonous plant of the nightshade family, Datura stramonium. 2 the prickly fruit of this. a thorn in one's flesh (or side) a constant annoyance. thornless adj. thornproof adj.
[ OE f. Gmc ]