fallout vs radioactive dust

fallout and radioactive dust both are nouns.

Word	Noun	Adjective	Verb	Adverb
fallout	Yes	No	No	No
radioactive dust	Yes	No	No	No

As nouns, fallout and radioactive dust are synonyms defined as:

fallout and radioactive dust: the radioactive particles that settle to the ground after a nuclear explosion

fallout (noun)	radioactive dust (noun)
any adverse and unwanted secondary effect	the radioactive particles that settle to the ground after a nuclear explosion
the radioactive particles that settle to the ground after a nuclear explosion