Ma'anar ƙamus na "gashin gadi" yana nufin ƙaƙƙarfan gashin gashi ko gashi wanda ke rufe jikin dabba kuma yana aiki don kare fatar dabba da kuma kare shi daga muhalli. Gashin karewa yawanci yakan fi tsayi da ƙorafi fiye da gashin ƙasa ko na biyu, kuma suna taimakawa wajen korar danshi, datti, da sauran abubuwa na waje. A wasu dabbobi, kamar karnuka da kuliyoyi, gashin gadi na iya zama alhakin ba wa dabbar kamanninta na musamman.