What is the designation for a space rock that is larger than a dust grain but smaller than an asteroid?

A space rock that is larger than a dust grain but smaller than an asteroid is correctly designated as a meteoroid. This term specifically refers to small celestial bodies that are in the solar system, and their size typically ranges from a grain of sand to a few meters in diameter.

Meteoroids are an important part of understanding the solar system as they can originate from comets or asteroids and provide insights into the early solar system's formation and evolution. When meteoroids enter the Earth's atmosphere and produce visible phenomena, they are referred to as meteors, and if they survive the journey and land on Earth, they are known as meteorites. The distinctions in terminology reflect both size and context of these objects as they interact with planetary atmospheres and surfaces.