LEMON

lem‧on

1 [uncountable and countable] a fruit with a hard yellow skin and sour juice:

a slice of lemon

Add a few drops of lemon juice.

2 [uncountable] British English a drink that tastes of lemons:

a glass of fizzy lemon

3 also lemon yellow [uncountable] a pale yellow colour

4 [countable] especially American English informal something that is useless because it fails to work or to work properly:

I soon realized the van was a lemon.

5 [countable] British English informal a silly person:

He just stood there looking like a real lemon.

Definition from the Longman Dictionary of Contemporary English
Advanced Learner's Dictionary.