killer whale vs orca

killer whale and orca both are nouns.

Word	Noun	Adjective	Verb	Adverb
killer whale	Yes	No	No	No
orca	Yes	No	No	No

As nouns, killer whale and orca are synonyms defined as:

killer whale and orca: predatory black-and-white toothed whale with large dorsal fin; common in cold seas

Other synonyms of killer whale include grampus, killer, Orcinus orca, sea wolf.

killer whale (noun)	orca (noun)
predatory black-and-white toothed whale with large dorsal fin; common in cold seas	predatory black-and-white toothed whale with large dorsal fin; common in cold seas