Learner's definition of APPLE
: a round fruit with red, yellow, or green skin and firm white flesh
— often used before another noun
◊ In figurative use, a bad apple or rotten apple is a bad member of a group who causes problems for the rest of the group.
A few bad apples cheated on the test, and now everyone has to take the test again.
One rotten apple ruined the day for the rest of us.
compare apples to apples/oranges
the apple of someone's eye
: a person or thing that someone loves very much