heirloom UK /ˈɛə.luːm/US /ˈɛɚ.lum/ noun2 •A valued possession that has been passed down through the generations. •An old crop variety that has been passed down through generations of farmers by seed saving and cultivation, in contrast to modern cultivars used in large-scale agriculture.My last trip to the market barely yielded enough unmealy heirlooms for a couple of salads. — 2009 formsheirlooms