foster parent vs defender

foster parent and defender both are nouns.

Word	Noun	Adjective	Verb	Adverb
foster parent	Yes	No	No	No
defender	Yes	No	No	No

As nouns, defender is a hypernym of foster parent; that is, defender is a word with a broader meaning than foster parent:

foster parent: a person who acts as parent and guardian for a child in place of the child's natural parents but without legally adopting the child
defender: a person who cares for persons or property

Other hypernyms of foster parent include guardian, protector, shielder.

foster parent (noun)	defender (noun)
a person who acts as parent and guardian for a child in place of the child's natural parents but without legally adopting the child	a person who cares for persons or property
	a fighter who holds out against attack