thorn

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Botany A modified branch in the form of sharp, woody spine.
2. n. Botany Any of various shrubs, trees, or woody plants bearing sharp, woody spines.
3. n. Any of various sharp, spiny protuberances; a prickle.
4. n. One that causes sharp pain, irritation, or discomfort: He is a thorn in my side.
5. n. The runic letter þ originally representing either sound of the Modern English th, as in the and thin, used in Old English and Middle English manuscripts.

Century Dictionary and Cyclopedia

1. n. A sharp excrescence on a plant: usually a branch, or the termination of a stem or branch, indurated, leafless, and attenuated to a point; a spine; a prickle. See spine, 1.
2. n. Figuratively, that which wounds or annoys; a cause of discomfort or irritation; a painful circumstance.
3. n. One of numerous thorny shrubs or trees, especially the members of the genus Cratægus, otherwise called haw. These are low trees or shrubs with abundant white blossoms, and small apple-like fruit sometimes edible. The wood is hard and close-grained—in some species, as the hawthorn, useful for turnery and even for wood-engraving. Several acacias and various other plants receive the name. See hawthorn, and specific names below.
4. n. In zoology, some sharp process, horn, or spine. See spine, 3.
5. n. In entomology, one of certain geometrid moths: an English book-name. The little thorn is Epione advenaria; the early thorn is Selenia illunaria.
6. n. In lace-making, a small pointed projection used to decorate the cordon-net, etc. Compare spine, 5.
7. n. The Anglo-Saxon letter þ, equivalent to th; also, the corresponding character in Icelandic.
8. n. In the United States, sometimes, the scarlet-fruited thorn.
9. n. See Macrocnemum.
10. To prick or pierce with or as with a thorn.
11. To fasten with a thorn.
12. Supplied (?).
13. To be supplied (?).

Wiktionary

1. n. A sharp protective spine of a plant.
2. n. A letter of the Latin alphabet (capital: Þ, small: þ), borrowed by Old English from the futhark to represent a dental fricative, then not distinguished from eth, but in modern use (in Icelandic and other languages, but no longer in English) used only for the voiceless dental fricative found in English thigh
3. v. To pierce with, or as if with, a thorn

GNU Webster's 1913

1. n. A hard and sharp-pointed projection from a woody stem; usually, a branch so transformed; a spine.
2. n. (Bot.) Any shrub or small tree which bears thorns; especially, any species of the genus Cratægus, as the hawthorn, whitethorn, cockspur thorn.
3. n. Fig.: That which pricks or annoys as a thorn; anything troublesome; trouble; care.
4. n. The name of the Anglo-Saxon letter �, capital form �. 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.
5. v. Poetic To prick, as with a thorn.

WordNet 3.0

1. n. a small sharp-pointed tip resembling a spike on a stem or leaf
2. n. a Germanic character of runic origin
3. n. something that causes irritation and annoyance