stock up vs overstock

stock up and overstock both are verbs.

Word	Noun	Adjective	Verb	Adverb
stock up	No	No	Yes	No
overstock	No	No	Yes	No

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

stock up: amass so as to keep for future use or sale or for a particular occasion or use
overstock: stock excessively

Other hyponyms of stock up include understock.

stock up (verb)	overstock (verb)
amass so as to keep for future use or sale or for a particular occasion or use	stock excessively