lemon meringue pie vs pie

lemon meringue pie and pie both are nouns.

Word	Noun	Adjective	Verb	Adverb
lemon meringue pie	Yes	No	No	No
pie	Yes	No	No	No

As nouns, pie is a hypernym of lemon meringue pie; that is, pie is a word with a broader meaning than lemon meringue pie:

lemon meringue pie (noun)	pie (noun)
pie containing lemon custard and topped with meringue	dish baked in pastry-lined pan often with a pastry top