piece vs rig up

piece is a noun but rig up is not a noun.

Word	Noun	Adjective	Verb	Adverb
piece	Yes	No	Yes	No
rig up	No	No	Yes	No

As verbs, rig up is a hyponym of piece; that is, rig up is a word with a more specific, narrower meaning than piece:

Other hyponyms of piece include comfit, confect, confection, confuse, jumble, mix up, reassemble, configure, compound.

piece (noun)	rig up (noun)
a separate part of a whole
game equipment consisting of an object used in playing certain board games
a portable gun
a work of art of some artistic value
an item that is an instance of some type
a distance
a musical work that has been created
an artistic or literary composition
an instance of some kind
a serving that has been cut from a larger portion
a portion of a natural object
a share of something
a period of indeterminate length (usually short) marked by some action or condition

piece (verb)	rig up (verb)
repair by adding pieces	erect or construct, especially as a temporary measure
eat intermittently; take small bites of
join during spinning
to join or unite the pieces of
create by putting components or members together