ensign vs emblem

ensign and emblem both are nouns.

Word	Noun	Adjective	Verb	Adverb
ensign	Yes	No	No	No
emblem	Yes	No	No	No

As nouns, emblem is a hypernym of ensign; that is, emblem is a word with a broader meaning than ensign:

Other hypernyms of ensign include flag, allegory.

ensign (noun)	emblem (noun)
colors flown by a ship to show its nationality	special design or visual object representing a quality, type, group, etc.
an emblem flown as a symbol of nationality	a visible symbol representing an abstract idea
a person who holds a commissioned rank in the United States Navy or the United States Coast Guard; below lieutenant junior grade