Basically, objects like
- Asteroids
- Meteoroids
- Meteors
- Meteorites
- Comets
- Etc.
As stated in the title, this also doesn't count human-made objects, such as
- Space junk
- Satellites,
- Space stations,
- Rockets or shuttles
- Other crafts
Nor does it count what I'll call here massive or unrelated objects , such as stuff like
- Dwarf planets
- Planetesimals
- Proto-planets
- Moons
- Etc.
Here's a visual representation of what I mean that I whipped up in a minute:
Best Answer
After a bit more research, I found my answer: small Solar System bodies (SSSB) is the official IAU term used for anything that is not a planet, dwarf planet, or moon.
In the article on the IAU site, "Pluto and the Developing Landscape of Our Solar System", they define it as:
For a more formal definition of the term, one can refer to the IAU's Resolution B5, made in 2006: