blend in vs meld

blend in is not a noun while meld is a noun.

Word	Noun	Adjective	Verb	Adverb
blend in	No	No	Yes	No
meld	Yes	No	Yes	No

As verbs, meld is a hypernym of blend in; that is, meld is a word with a broader meaning than blend in:

Other hypernyms of blend in include blend, coalesce, combine, commingle, conflate, flux, fuse, immix, merge, mix.

blend in (noun)	meld (noun)
	a form of rummy using two decks of cards and four jokers; jokers and deuces are wild; the object is to form groups of the same rank

blend in (verb)	meld (verb)
cause (something) to be mixed with (something else)	mix together different elements
blend or harmonize	lose its distinct outline or shape; blend gradually
	announce for a score; of cards in a card game