planosporeBot.|ˈplænəʊspɔə(r)| [f. plano-2 + spore.] A motile zoospore. 1950E. A. Bessey Morphol. & Taxon. Fungi i. 5 The motile naked zoospores..may be called planospores.1970J. Webster Introd. Fungi i. 68 The zoospore is sometimes termed a planospore.