coastguard vs military service

coastguard and military service both are nouns.

Word	Noun	Adjective	Verb	Adverb
coastguard	Yes	No	No	No
military service	Yes	No	No	No

As nouns, military service is a hypernym of coastguard; that is, military service is a word with a broader meaning than coastguard:

coastguard: a military service responsible for the safety of maritime traffic in coastal waters
military service: a force that is a branch of the armed forces

Other hypernyms of coastguard include armed service, service.

coastguard (noun)	military service (noun)
a military service responsible for the safety of maritime traffic in coastal waters	land tenure by service in the lord's army
	a force that is a branch of the armed forces