fuse vs mix in

fuse is a noun but mix in is not a noun.

Word	Noun	Adjective	Verb	Adverb
fuse	Yes	No	Yes	No
mix in	No	No	Yes	No

As verbs, mix in is a hyponym of fuse; that is, mix in is a word with a more specific, narrower meaning than fuse:

fuse (noun)	mix in (noun)
any igniter that is used to initiate the burning of a propellant
an electrical device that can interrupt the flow of electrical current when it is overloaded

fuse (verb)	mix in (verb)
mix together different elements	cause (something) to be mixed with (something else)
make liquid or plastic by heating	add as an additional element or part
become plastic or fluid or liquefied from heat
equip with a fuse; provide with a fuse