sea king vs sea robber

sea king and sea robber both are nouns.

Word	Noun	Adjective	Verb	Adverb
sea king	Yes	No	No	No
sea robber	Yes	No	No	No

As nouns, sea robber is a hypernym of sea king; that is, sea robber is a word with a broader meaning than sea king:

sea king: a Viking pirate chief
sea robber: someone who robs at sea or plunders the land from the sea without having a commission from any sovereign nation

Other hypernyms of sea king include buccaneer, pirate, sea rover.

sea king (noun)	sea robber (noun)
a Viking pirate chief	someone who robs at sea or plunders the land from the sea without having a commission from any sovereign nation