thorn (thôrn)n.1. Botany a. A modified branch in the form of a sharp woody structure.b. Any of various other sharp protuberances, such as a spine.c. Any of various shrubs, trees, or woody plants bearing such sharp structures.2. Any of various sharp protuberances on an animal.3. One that causes sharp pain, irritation, or discomfort: He is a thorn in my side.4. The runic letter þ, used in Old English, Middle English, and Old Norse manuscripts to represent both the voiceless sound (th) of Modern English thin and the voiced sound (th) of Modern English this, and in modern Icelandic orthography to represent the voiceless sound (th).[Middle English, from Old English.]thorn?less adj.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.thorn (???n) n1. (Botany) a sharp pointed woody extension of a stem or leaf. Compare prickle12. (Plants) a. any of various trees or shrubs having thorns, esp the hawthornb. the wood of any of these plants3. (Animals) short for thorn moth4. (Letters of the Alphabet (Foreign)) 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 theta5. (Letters of the Alphabet (Foreign)) this same character as used in Old and Middle English as an alternative to edh, but indistinguishable from it in function or sound. Compare edh6. (Zoology) zoology any of various sharp spiny parts7. a source of irritation (esp in the phrases a thorn in one’s side or flesh)[Old English; related to Old High German dorn, Old Norse thorn] ?thornless adjThorn (to?rn) n (Placename) the German name for Toru?Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014thorn (??rn) n. 1. a hard, sharp outgrowth on a plant, esp. a sharp-pointed aborted branch. 2. a thorny tree or shrub, as the hawthorne. 3. the wood of such a plant. 4. a runic character (þ), borrowed into the Latin alphabet and used to represent the initial th sounds of thin and they in Old English and of thin in modern Icelandic. 5. a source of continual irritation, trouble, or discomfort (esp. in the phrase thorn in one’s side or flesh). v.t. 6. to prick with a thorn; vex. [before 900; Middle English, Old English, c. Old Saxon, Old High German, Old Norse thorn, Gothic thaurnus] thorn?less, adj. thorn?like`, adj. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.thorn (thôrn)1. A short, hard, pointed part of a stem or branch of a woody plant.2. Any of various plants bearing thorns.Usage It hardly makes a difference whether you get pricked by a thorn or a spine?it hurts just the same. But a person who studies plants might think there was a difference. Scientifically speaking, a thorn is a hard, pointed part of a stem or branch of a woody plant. While the word spine is used loosely to refer to any hard, pointed structure on a plant, it more properly refers to a leaf that has evolved into a narrow, sharp projection to conserve water and protect the stem, which stores water. Thus a cactus has spines but not thorns, and a rose bush and hawthorn have thorns but not spines.The American Heritage® Student Science Dictionary, Second Edition. Copyright © 2014 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.