grapefruit /ˈɡɹeɪ̯pfɹuːt/ noun3 •The large spherical tart fruit produced by this tree. •The tree of the species Citrus paradisi, a hybrid of Citrus maxima and sweet orange. •[usually plural] (vulgar) Large breasts; by extension, a woman with large breasts.Cupping her grapefruits in her hands, she closed her eyes and imagined her date grasping them, exploring their size, weight, and firmness. formsgrapefruits