dumdum bullet vs bullet

dumdum bullet and bullet both are nouns.

Word	Noun	Adjective	Verb	Adverb
dumdum bullet	Yes	No	No	No
bullet	Yes	No	No	No

As nouns, bullet is a hypernym of dumdum bullet; that is, bullet is a word with a broader meaning than dumdum bullet:

dumdum bullet: a soft-nosed small-arms bullet that expands when it hits a target and causes a gaping wound
bullet: a projectile that is fired from a gun

Other hypernyms of dumdum bullet include slug.

dumdum bullet (noun)	bullet (noun)
a soft-nosed small-arms bullet that expands when it hits a target and causes a gaping wound	(baseball) a pitch thrown with maximum velocity
	a projectile that is fired from a gun
	a high-speed passenger train