outwork vs defensive structure

outwork and defensive structure both are nouns.

Word	Noun	Adjective	Verb	Adverb
outwork	Yes	No	No	No
defensive structure	Yes	No	No	No

As nouns, defensive structure is a hypernym of outwork; that is, defensive structure is a word with a broader meaning than outwork:

outwork: subsidiary defensive structure lying outside the main fortified area
defensive structure: a structure used to defend against attack

Other hypernyms of outwork include defence, defense.

outwork (noun)	defensive structure (noun)
subsidiary defensive structure lying outside the main fortified area	a structure used to defend against attack