BSL Astronomy Glossary - asteroid - definition
Definition: Asteroids are large lumps of rock in space. They are found in the Asteroid Belt, which lies between the inner and outer planets. Asteroids range in length from 100 metres to thousands of metres and they are usually irregularly shaped. One example of an asteroid is Itokawa, which is 150 metres long. The video clip shows a model of Itokawa, much smaller than the real asteroid but with a similar shape and appearance.