WMD vs atomic weapon

WMD and atomic weapon both are nouns.

Word	Noun	Adjective	Verb	Adverb
WMD	Yes	No	No	No
atomic weapon	Yes	No	No	No

As nouns, atomic weapon is a hyponym of WMD; that is, atomic weapon is a word with a more specific, narrower meaning than WMD:

WMD: a weapon that kills or injures civilian as well as military personnel (nuclear and chemical and biological weapons)
atomic weapon: a weapon of mass destruction whose explosive power derives from a nuclear reaction

WMD (noun)	atomic weapon (noun)
a weapon that kills or injures civilian as well as military personnel (nuclear and chemical and biological weapons)	a weapon of mass destruction whose explosive power derives from a nuclear reaction