: any of two families (Pospiviroidae and Avsunviroidae) of subviral particles that consist of a small single-stranded RNA arranged in a closed loop without a protein shell and that replicate in their host plants where they may or may not be pathogenic
Examples of viroid in a Sentence
Recent Examples on the Web
Originally considered pathogenic, other viroid infections were found to be symptomless or latent.
—
Discover Magazine, 31 Jan. 2025
Given the ubiquity of viroids in the plant world, finding something similar in bacteria makes perfect sense, says Hefferon, who studies disease-causing viroids in commercial crops such as potatoes.
—Joanna Thompson, Scientific American, 16 Feb. 2024
Like viruses, viroids reproduce by invading healthy cells and reprogramming them to duplicate the viroid’s genetic makeup instead of the cell’s own.
—Daniel E. Slotnik, New York Times, 8 May 2023
For now, the problem of the hop latent viroid has largely fallen to growers themselves.
—Dan Adams, BostonGlobe.com, 3 Dec. 2022
The agency has also found diseases known to occur in China, called pospiviroid and spindle tuber viroid, in seeds, as well as a few pests of significance: an immature wasp and a larval seed beetle.
—Jon Emont and Jesse Newman, WSJ, 5 Sep. 2020
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Discover Magazine, 31 Jan. 2025
Given the ubiquity of viroids in the plant world, finding something similar in bacteria makes perfect sense, says Hefferon, who studies disease-causing viroids in commercial crops such as potatoes.
—Joanna Thompson, Scientific American, 16 Feb. 2024
Like viruses, viroids reproduce by invading healthy cells and reprogramming them to duplicate the viroid’s genetic makeup instead of the cell’s own.
—Daniel E. Slotnik, New York Times, 8 May 2023
For now, the problem of the hop latent viroid has largely fallen to growers themselves.
—Dan Adams, BostonGlobe.com, 3 Dec. 2022
The agency has also found diseases known to occur in China, called pospiviroid and spindle tuber viroid, in seeds, as well as a few pests of significance: an immature wasp and a larval seed beetle.
—Jon Emont and Jesse Newman, WSJ, 5 Sep. 2020
Cite this Entry
“Viroid.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/viroid. Accessed 18 Jul. 2025.
Copy CitationMedical Definition
viroid
1 of 2 noun
vi·roid
ˈvī-ˌrȯid 
1
: a hypothetical symbiont resembling a virus that was formerly held to be present in cells, to be favorable to the host, and to tend to mutate to a virus
2
: any of two families (Pospiviroidae and Avsunviroidae) of subviral particles that consist of a small single-stranded RNA arranged in a closed loop without a protein shell and that replicate in their host plants where they may or may not be pathogenic
viroid
2 of 2 adjective1
: caused by a virus
viroid pneumonia
2
: of or relating to viroids
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