piggy bank vs coin bank

piggy bank and coin bank both are nouns.

Word	Noun	Adjective	Verb	Adverb
piggy bank	Yes	No	No	No
coin bank	Yes	No	No	No

As nouns, coin bank is a hypernym of piggy bank; that is, coin bank is a word with a broader meaning than piggy bank:

piggy bank: a child's coin bank (often shaped like a pig)
coin bank: a container (usually with a slot in the top) for keeping money at home

Other hypernyms of piggy bank include bank, money box, savings bank.

piggy bank (noun)	coin bank (noun)
a child's coin bank (often shaped like a pig)	a container (usually with a slot in the top) for keeping money at home