What does apple pie mean?
The definition of apple pie
Ap”ple pie`.
A pie made of apples (usually sliced or stewed) with spice and sugar. Apple-pie bed, a bed in which, as a joke, the sheets are so doubled (like the cover of an apple turnover) as to prevent any one from getting at his length between them. Halliwell, Conybeare.

— Apple-pie order, perfect order or arrangement. [Colloq.] Halliwell.