Polyhedron concave siffa ce mai girma uku wacce ke da aƙalla kwana ɗaya na ciki wanda ya fi digiri 180, yana sa siffar ta bayyana mai lanƙwasa ko ta shiga ciki. Kalmar “polyhedron” tana nufin wani abu mai ƙarfi mai ɗauke da fiskoki, kuma kalmar “concave” na nufin cewa saman yana lanƙwasa a ciki, maimakon yin kumbura a waje kamar fili. Concave polyhedra na iya samun kowane adadin fuskoki, gefuna, da madaidaita, kuma ana iya haɗa su da kowane haɗin polygons. Misalai na concave polyhedra sun haɗa da wasu nau'ikan prisms marasa tsari, pyramids, da dodecahedrons.