n. In bot.:n. As used by Linnæus, a leaf, especially the leaf of a palm or fern.n. Now, specifically, a leaf of a fern or other cryptogam, the thallus of a lichen, or any other leaf-like expansion which includes both stem and foliage, as the disk of Lemna.n. In zoology, the foliaceous or leaf-like expansion of certain animal organisms, as of various polyzoans and actinozoans, which resemble plants in the mode of growth of the polypstock.