Any of various tree-borne fruits or vegetables especially considered as resembling an apple; also (with qualifying words) used to form the names of other specific fruits such as custard apple, rose apple, thorn apple etc. [from 9th c.]
The fruit of the Tree of Knowledge, eaten by Adam and Eve according to post-Biblical Christian tradition; the forbidden fruit. [from 11th c.]
A tree of the genus Malus, especially one cultivated for its edible fruit; the apple tree. [from 15th c.]