grampus vs killer whale

grampus and killer whale both are nouns.

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

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

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

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

grampus (noun)	killer whale (noun)
slaty-grey blunt-nosed dolphin common in northern seas	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