mustard gas vs mustard agent

mustard gas and mustard agent both are nouns.

Word	Noun	Adjective	Verb	Adverb
mustard gas	Yes	No	No	No
mustard agent	Yes	No	No	No

As nouns, mustard gas and mustard agent are synonyms defined as:

mustard gas and mustard agent: a toxic war gas with sulfide based compounds that raises blisters and attacks the eyes and lungs; there is no known antidote

Other synonyms of mustard gas include blistering agent, dichloroethyl sulfide, sulfur mustard.

mustard gas (noun)	mustard agent (noun)
a toxic war gas with sulfide based compounds that raises blisters and attacks the eyes and lungs; there is no known antidote	a toxic war gas with sulfide based compounds that raises blisters and attacks the eyes and lungs; there is no known antidote