dullard vs gasbag

dullard and gasbag both are nouns.

Word	Noun	Adjective	Verb	Adverb
dullard	Yes	No	No	No
gasbag	Yes	No	No	No

As nouns, gasbag is a hyponym of dullard; that is, gasbag is a word with a more specific, narrower meaning than dullard:

Other hyponyms of dullard include windbag, nudnick, nudnik, platitudinarian, stuffed shirt.

dullard (noun)	gasbag (noun)
a person who evokes boredom	the bag containing the gas in a balloon
a person who is not very bright	a boring person who talks a great deal about uninteresting topics