Is pressure equalization "diffusion"?
Its not diffusion, it's effusion. The difference is that with diffusion the particles/molecules are migrating through a permeable medium where as for effusion the particles/molecules are migrating through a pore/hole.

For example, a scent travelling across a room is diffuision, a scent from the room traveling outside is effusion. Also fun fact: the helium escaping through a balloon skin is actually effusion not diffusion.

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Side note: I am starting to flashback to all the times my thermo professors said diffusion when they meant effusion.