killer whale vs grampus

killer whale and grampus both are nouns.

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

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

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

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

killer whale (noun)	grampus (noun)
predatory black-and-white toothed whale with large dorsal fin; common in cold seas	slaty-grey blunt-nosed dolphin common in northern seas
	predatory black-and-white toothed whale with large dorsal fin; common in cold seas