In botany and zoology, root-like; resembling a root.n. In botany, a filamentous organ resembling a root, but of simple structure, found on compound thalli of all kinds, and on the stems of the Muscineæ.n. Rhizoids are numerously produced, and their function is the attachment of the plant to the substratum. The older term was rhizina. See cut under prothallium.