grapefruit: citrus tree bearing large round edible fruit having a thick yellow rind and juicy somewhat acid pulp
citrus: any of numerous tropical usually thorny evergreen trees of the genus Citrus having leathery evergreen leaves and widely cultivated for their juicy edible fruits having leathery aromatic rinds
mycenaean civilization: the late bronze-age culture of Mycenae that flourished 1400-1100 BC