Webster's Revised Unabridged Dictionary · 1913

Thorn

Thorn , noun

[Anglo-Saxon þorn; akin to Old Saxon & OFries. thorn, Dutch doorn, German dorn, Danish torn, Swedish torne, Icelandic þorn, Gothic þaúrnus; compare Pol. tarn, Russ. tern' the blackthorn, ternie thorns, Sanskrit trna grass, blade of grass. r53.]

1.
A hard and sharp-pointed projection from a woody stem; usually, a branch so transformed; a spine.
2.
(Botany) Any shrub or small tree which bears thorns; especially, any species of the genus Crataegus, as the hawthorn, whitethorn, cockspur thorn.
3.
Figuratively: That which pricks or annoys as a thorn; anything troublesome; trouble; care.
There was given to me a thorn in the flesh, the messenger of Satan to buffet me. — 2 Cor. xii. 7
The guilt of empire, all its thorns and cares, Be only mine. — Southern
4.
The name of the Anglo-Saxon letter {not transcribed}, capital form {not transcribed}. It was used to represent both of the sounds of English th, as in thin, then. So called because it was the initial letter of thorn, a spine.
Collocations (5)
Thorn apple (Botany) , Jamestown weed.
Thorn broom (Botany) , a shrub that produces thorns.
Thorn hedge , a hedge of thorn-bearing trees or bushes.
Thorn devil (Zoology) , See Moloch, 2.
Thorn hopper (Zoology) , a tree hopper (Thelia crataegi) which lives on the thorn bush, apple tree, and allied trees.

Thorn , transitive verb

To prick, as with a thorn. [Poetic]
I am the only rose of all the stock That never thorn'd him. — Tennyson