from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. An infectious particle, similar to but smaller than a virus, that consists solely of a strand of RNA and is capable of causing disease in plants.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. plant pathogens, of the order Viroidales, that consist of just a short section of RNA but without the protein coat typical of viruses
  • n. human pathogen, most notably hepatitis D.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. the smallest of viruses; a plant virus with its RNA arranged in a circular chromosome without a protein coat


Sorry, no etymologies found.


  • Locking her arms around the doctor despite his indignant yelp, she whirled him away from the entrance and beyond the snaking grasp of one of the viroid creatures.

    Time's Enemy

  • "You've got a shipload of viroid life-forms outside draining our power systems, and I've got a Trill symbiont in the infirmary who says it can help us."

    Time's Enemy

  • "What we have here isn't an Andorian who's been infected by some alien virus's DNAwe have a viroid life-form that's absorbed an Andorian's genetic code for its own selective usage."

    Time's Enemy

  • For the moment, symptomatic treatment was in order, then detailed analysis of the virus or viroid.

    Dark Mirror

  • If you find so much as a pre-biotic spherule, a pseudo-membranous configuration, even a viroid aggregate, the show's off.


  • In fact, it turned out that a disease that had nearly wiped out the American mum industry in the mid-1950s had been caused by a viroid of their own.

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  • The enzymes use the viroid as a template to make a new viroid progeny.

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  • Yet that's enough genetic information to let a viroid infect a plant and replicate itself by taking advantage of the enzymes the plant uses to replicate its DNA.

    *Science* Blog Portal

  • (For some reason, no one has found an animal viroid.)

    *Science* Blog Portal

  • Vacuolar apoplastic localization leaf tissue tomato plants infested citrus exocortis viroid; vitro synthesis processing.

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