stuff vs overstuff

stuff is a noun but overstuff is not a noun.

Word	Noun	Adjective	Verb	Adverb
stuff	Yes	No	Yes	No
overstuff	No	No	Yes	No

As verbs, overstuff is a hyponym of stuff; that is, overstuff is a word with a more specific, narrower meaning than stuff:

Other hyponyms of stuff include chock up, cram, jam, jampack, ram, wad, fill out, pad.

stuff (noun)	overstuff (noun)
miscellaneous unspecified objects
unspecified qualities required to do or be something
a critically important or characteristic component
senseless talk
information in some unspecified form
informal terms for personal possessions
the tangible substance that goes into the makeup of a physical object

stuff (verb)	overstuff (verb)
fill with a stuffing while cooking	stuff too much
fill tightly with a material
treat with grease, fill, and prepare for mounting
overeat or eat immodestly; make a pig of oneself
cram into a cavity
obstruct
press or force