peppermint tree noun2 •(Australia) Any of several species of eucalypt which yield an essential oil that smells of peppermint, especially a member of the stringybark group.Maybe even a peppermint tree, broad and moppish and spicy like the ones lining Eliza's street. — 2007 •(Australia) A tree of the family Myrtaceae bearing leaves that smell of peppermint, especially willow myrtle, Agonis flexuosa, often colloquially called a peppy. formspeppermint trees