thorn

¹ American  

[thawrn] / θɔrn /

noun

1. a sharp excrescence on a plant, especially a sharp-pointed aborted branch; spine; prickle.

2. any of various thorny shrubs or trees, especially the hawthorns belonging to the genus Crataegus, of the rose family.

3. the wood of any of these trees.

4. a runic character (þ), borrowed into the Latin alphabet and representing the initial th sounds in thin and they in Old English, or thin in modern Icelandic.

5. something that wounds, annoys, or causes discomfort.

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verb (used with object)

1. to prick with a thorn; vex.

idioms

1. thorn in one's side / flesh, a source of continual irritation or suffering.

   That child is a thorn in the teacher's side.

Thorn ² American  

[tawrn] / tɔrn /

noun

1. German name of Toruń.

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thorn ¹ British  

/ θɔːn /

noun

1. a sharp pointed woody extension of a stem or leaf Compare prickle

2. 1. any of various trees or shrubs having thorns, esp the hawthorn

   2. the wood of any of these plants

3. short for thorn moth

4. a Germanic character of runic origin Þ used in Old and Modern Icelandic to represent the voiceless dental fricative sound of th, as in thin, bath. Its use in phonetics for the same purpose is now obsolete See theta

5. this same character as used in Old and Middle English as an alternative to edh, but indistinguishable from it in function or sound Compare edh

6. zoology any of various sharp spiny parts

7. a source of irritation (esp in the phrases a thorn in one's side or flesh )

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Thorn ² British  

/ toːrn /

noun

1. the German name for Toruń

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thorn Scientific  

/ thôrn /

1. A short, hard, pointed part of a stem or branch of a woody plant.

2. Compare spine

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Other Word Forms

• thornless adjective
• thornlike adjective
• unthorn verb (used with object)

Etymology

Origin of thorn

before 900; Middle English (noun), Old English; cognate with Dutch doorn, German Dorn, Old Norse thorn, Gothic thaurnus

Explanation

A thorn is a sharp spike that protrudes from the stem of a plant. Roses are famous for having the sweetest fragrance and the sharpest thorns. Literal thorns, found on bushes and other plants, serve to protect plants from animals that might like to eat them. A "thorn in one's side" is an annoyance or problem: "My neighbors are a thorn in my side, with their constant loud music and crazy parties!" The source of this figurative definition is the Bible's "thorn in the flesh."

Example Sentences

Anthropic’s new model, Claude Mythos, has been the latest thorn in the side of the software sector.

From MarketWatch • Apr. 16, 2026

Manchester City have been a thorn in Arsenal's side in their quest for silverware.

From BBC • Apr. 4, 2026

Dutch Bros, a coffee and beverage chain still unknown in many parts of the country, is becoming a thorn in Starbucks’s side.

From The Wall Street Journal • Mar. 1, 2026

The data highlights that inflation remains a thorn in the side of the RBA, and that an increase in interest rates at the start of February is highly likely to be repeated in coming months.

From The Wall Street Journal • Feb. 25, 2026

It is intensely shy, nests in bramble and thorn, eats large insects and fairies, flies only in heavy rain and otherwise remains hidden in its tear-shaped nest.

From "Fantastic Beasts and Where to Find Them" by J.K. Rowling