View your list of saved words. (You can log in using Facebook.)
Definition of VIROID
: 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
Infectious particle that is smaller than any of the known viruses. The particle consists of an extremely small circular RNA molecule that lacks the protein coat of a virus. Viroids appear to be transmitted mechanically from one cell to another through cellular debris. They are of much interest because of their subviral nature and their unknown mode of action. Viroids are agents of certain plant diseases; whether they occur in animal cells is uncertain.