stump vs mix up

stump is a noun but mix up is not a noun.

Word	Noun	Adjective	Verb	Adverb
stump	Yes	No	Yes	No
mix up	No	No	Yes	No

As verbs, stump and mix up are synonyms defined as:

stump (noun)	mix up (noun)
(cricket) any of three upright wooden posts that form the wicket
a platform raised above the surrounding level to give prominence to the person on it
the part of a limb or tooth that remains after the rest is removed
the base part of a tree that remains standing after the tree has been felled

stump (verb)	mix up (verb)
remove tree stumps from	cause to be perplexed or confounded
cause to be perplexed or confounded	assemble without order or sense
travel through a district and make political speeches
walk heavily