Kalmar “butterfly nut” tana nufin wani nau’in goro ko na’ura mai lanƙwasa fukafukai biyu ko “kunnuwa” waɗanda za a iya jujjuya su da hannu cikin sauƙi don ƙara ko sassauta shi. An ce siffar goro yana kama da na malam buɗe ido, don haka sunan. Ana amfani da goro na malam buɗe ido a aikace inda goro ya buƙaci a iya cirewa cikin sauƙi ko daidaitawa, kamar a cikin kayan aikin mota ko masana'antu.