Definition of plant-animal in US English:

plant-animal

noun

rare
  • An organism which has characteristics of both an animal and a plant. In early use: †a plant which is supposed to resemble an animal in some respect; = "zoophyte" (obsolete). In later use chiefly: an animal which resembles a plant in form, usually sessile and having a branching or radiating structure.

Origin

Early 17th century; earliest use found in Thomas Lodge (1558–1625), author and physician. From plant + animal, after French † plant-animal (1602 in the source translated in quot. 1621 at sense 1; from post-classical Latin plantanimal (G. Budé Annot. in Pandectas), itself after Hellenistic Greek ζωόϕυτον).