buster vs youngster

buster and youngster both are nouns.

Word	Noun	Adjective	Verb	Adverb
buster	Yes	No	No	No
youngster	Yes	No	No	No

As nouns, youngster is a hypernym of buster; that is, youngster is a word with a broader meaning than buster:

Other hypernyms of buster include child, fry, kid, minor, nestling, nipper, shaver, small fry, tiddler, tike, tyke.

buster (noun)	youngster (noun)
a person (or thing) that breaks up or overpowers something	a young person of either sex
a person who breaks horses
a robust child
an informal form of address for a man
a person born in the generation following the baby boom when the birth rate fell dramatically