pirate vs looter

pirate and looter both are nouns.

Word	Noun	Adjective	Verb	Adverb
pirate	Yes	No	Yes	No
looter	Yes	No	No	No

As nouns, looter is a hypernym of pirate; that is, looter is a word with a broader meaning than pirate:

pirate: someone who robs at sea or plunders the land from the sea without having a commission from any sovereign nation
looter: someone who takes spoils or plunder (as in war)

Other hypernyms of pirate include despoiler, freebooter, pillager, plunderer, raider, spoiler.

pirate (noun)	looter (noun)
a ship that is manned by pirates	someone who takes spoils or plunder (as in war)
someone who robs at sea or plunders the land from the sea without having a commission from any sovereign nation
someone who uses another person's words or ideas as if they were his own

pirate (verb)	looter (verb)
take arbitrarily or by force
copy illegally; of published material