submenu vs hierarchical menu

submenu and hierarchical menu both are nouns.

Word	Noun	Adjective	Verb	Adverb
submenu	Yes	No	No	No
hierarchical menu	Yes	No	No	No

As nouns, submenu and hierarchical menu are synonyms defined as:

submenu and hierarchical menu: a secondary menu that appears while you are holding the cursor over an item on the primary menu

Other synonyms of submenu include cascading menu.

submenu (noun)	hierarchical menu (noun)
a secondary menu that appears while you are holding the cursor over an item on the primary menu	a secondary menu that appears while you are holding the cursor over an item on the primary menu