killer vs killer whale

killer and killer whale both are nouns.

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

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

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

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

killer (noun)	killer whale (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
a difficulty that is hard to deal with
someone who causes the death of a person or animal
the causal agent resulting in death