Kalmar "gashin baya" na nufin wata kafa ta baya ko ƙafar dabba mai ƙafafu huɗu, yawanci ana amfani da ita don tallafi da motsi. A cikin kashin baya, irin su dabbobi masu shayarwa, sashin baya ya hada da kasusuwa kamar femur, tibia, fibula, da kasusuwan kafa, da tsokoki, tendons, da ligaments wadanda ke ba da damar motsi iri-iri, kamar gudu, tsalle. , da hawan. Har ila yau, a wasu lokuta ana kiran gaɓar gaɓa a matsayin "ƙafar baya" ko "ƙafa ta baya."