Are meteors and meteorites considered "Small Solar System Bodies"?
Your question is really well answered by this article at the Encyclopedia Britannica website, written by Prof. Ed Tedesco of the Planetary Science Institute.

Two quotes that resonate well are...

The small bodies populate the solar system in vast numbers and include ... the fragments of these bodies—commonly called meteoroids—over a continuum of sizes down to microscopic grains known as interplanetary dust particles or micrometeoroids.

And...

The term small body is sometimes restricted to objects that can be observed telescopically while still outside Earth’s atmosphere. In practice, this results in a lower limit of a few metres on the diameter of a small body.

So in general you can assume that anything other than the Sun, planets, minor planets, and their moons is a small solar system body. But in practice it makes sense to limit the minimum size for a SSSB, and the "observable telescopically" caveat provides that limit so that we don't have to include single molecules or one grain of sand in the list.