Lemon

1. a pale yellow oval citrus fruit with thick skin and fragrant, acidic juice.

   the juice of seven lemons

   garnish with a slice of lemon

   lemon juice

2. the evergreen citrus tree which produces lemons, widely cultivated in warm climates.
3. a pale yellow colour.

   a lemon T-shirt

4. an unsatisfactory or feeble person or thing.

   car-makers cannot afford to create lemons

Middle English: via Old French limon (in modern French denoting a lime) from Arabic līmūn (a collective term for fruits of this kind); compare with lime².