From Longman Dictionary of Contemporary Englishgrapefruitgrape‧fruit /ˈɡreɪpfruːt/ ●●● S3 noun [countable, uncountable] 
DFFHBPa round yellow citrus fruit with a thick skin, like a large orange
DFFHBPa round yellow citrus fruit with a thick skin, like a large orangeExamples from the Corpus
grapefruit• They're a cross between a grapefruit and a tangerine.• Me, trying to ignore it all while I section a grapefruit for the teen-ager.• If not eating both grapefruit halves at the same time, keep the remaining filling in the bowl until ready to use.• Whisk together remaining ingredients except grapefruit slices and mint leaves.• A mature grapefruit tree can produce 250 grapefruit.• The hamburger is gone and more grapefruit juice has arrived.• The sweeter, more nutritious, relatively new varieties of ruby grapefruit made for fine eating at home.• Garnish with grapefruit slices and mint leaves.Origin grapefruit (1800-1900) Because it grows in bunches, like grapes 