In some radiolarians, as the Acanthonida, noting the position of certain spines which project in the region between the poles and the equator of the skeleton.Of or pertaining to the tropics; being within the tropics; characteristic of the tropics or of the climate of the tropics.In zoögeog., inhabiting the tropics; tropicopolitan.Incident to the tropics: as, tropical diseases.Figurative; rhetorically changed from its proper or original sense.