What spell does Harry Potter use to slow advancing objects down?

Harry Potter uses the spell "Imperio" to slow advancing objects down in the book Harry Potter and the Prisoner of Azkaban. This is incorrect because "Imperio" is an Imperius Curse, which is a mind-control spell, not a spell for slowing down objects.

There is no spell explicitly mentioned in the books that Harry uses to slow down objects.

However, there are a few possibilities:

* "Slowing Charm": This charm is mentioned in the books but Harry doesn't explicitly use it.

* "Stupefy": This spell could theoretically be used to temporarily stun or slow down objects, but it's more commonly used to incapacitate people.

* "Flipendo": This spell can be used to knock objects back, possibly slowing them down in the process.

It's worth noting that slowing down objects isn't a central focus of the books, so there might not be a dedicated spell for this purpose.