thorn / [unvoicedth]ôrn/ • n. 1. a stiff, sharp-pointed, straight or curved woody projection on the stem or other part of a plant. ∎ fig. a source of discomfort, annoyance, or difficulty; an irritation or an obstacle: the issue has become a thorn in renewing the peace talks. See also a thorn in someone's side below. 2. (also thorn bush or thorn tree) a thorny bush, shrub, or tree, esp. a hawthorn. 3. an Old English and Icelandic runic letter, Þ or þ, representing the dental fricatives / [voicedth]/ and / [unvoicedth]/ . In English it was eventually superseded by the digraph th. Compare with eth. PHRASES: a thorn in someone's side (or flesh) a source of continual annoyance or trouble: the pastor has long been a thorn in the side of the regime.DERIVATIVES: thorn·less adj. (in sense 1).thorn·proof / -ˌproōf/ adj. (in sense 1).

THORN. The name of a runic LETTER and its manuscript and printed form þ, used in OLD ENGLISH and MIDDLE ENGLISH for voiced and voiceless th. In late medieval times, its form became similar to, and in some handwriting identical with, y, with the result that ye, yis, yat, etc., were used (well into modern times) as variants of the, this, that, etc.: the origin of ye for the in such phrases and names as Ye Olde Englishe Tea Shoppe (often facetiously pronounced ‘ye oldy Englishy tea shoppy’). See ETH, RUNE, T.

thorn sharp-pointed process on a plant; thornbearing plant. OE. þorn = OS. thorn (Du. doorn), (O)HG. dorn, ON. þorn, Goth. þaurnus :- Gmc. þurnuz :- IE. *tṛnus, f. *tṛn- tern-, repr. also by OIr. tráinín small stalk of grass, OSl. trŭnŭ thorn, Skr. tṛ́ṇa- grass-stalk, Gr. térnax cactus prickle.
Hence thorny (-Y1) OE. þorniġ.

thorn2 thorn in the flesh a constant affliction, a source of continual trouble and annoyance; often with biblical allusion to 2 Corinthians 12:7. The phrase thorn in the side is also frequently used.

See also crown of thorns, no rose without a thorn.

thorn A hard side stem with a sharp point at the tip, replacing the growing point. In some plants the development of thorns and subsequent suppression of the growing points may be a response to dry conditions. Examples are the thorns of gorse and hawthorn. Compare prickle; spine.