Consider the following sentence:
"They even stuffed many items behind our shed out back."
In this sense, what does 'stuffed' mean?
tr. 2. a.
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https://www.ahdictionary.com/word/search.html?q=stuff
v.tr. 2.a. To place forcefully into a container or space; thrust: stuffed laundry into the bag.
It means to fill/pack a space with something.
Take a look at entry #1 for "stuff" as a verb in the link below.
https://www.lexico.com/definition/stuff
Are you sure the sentence didn't say "out the back"?