a tree of a genus that includes citron, lemon, lime, orange, and grapefruit. Native to Asia, citrus trees are widely cultivated in warm countries for their fruit, which has juicy flesh and a pulpy rind.
Genus Citrus, family Rutaceae
(also citrus fruit) a fruit from a citrus tree: [as modifier]:citrus extracts
early 19th century: Latin, literally 'citron tree, thuja'