concert grand vs grand piano

concert grand and grand piano both are nouns.

Word	Noun	Adjective	Verb	Adverb
concert grand	Yes	No	No	No
grand piano	Yes	No	No	No

As nouns, grand piano is a hypernym of concert grand; that is, grand piano is a word with a broader meaning than concert grand:

concert grand: a grand piano suitable for concert performances
grand piano: a piano with the strings on a horizontal harp-shaped frame; usually supported by three legs

Other hypernyms of concert grand include grand.

concert grand (noun)	grand piano (noun)
a grand piano suitable for concert performances	a piano with the strings on a horizontal harp-shaped frame; usually supported by three legs