What is defined as a chunk of rock or metal orbiting in space, not exceeding a meter in size?

The term for a chunk of rock or metal orbiting in space that does not exceed a meter in size is a meteoroid. This classification specifically refers to smaller space debris relative to other celestial objects. When these objects enter the Earth's atmosphere and produce a visible streak of light, they are referred to as meteors. If they survive their passage through the atmosphere and reach the Earth's surface, they are recognized as meteorites.

The definitions of the other terms highlight their distinctions: a coma is the nebulous envelope around the nucleus of a comet, and asteroids are larger rocky bodies, typically larger than a meter, that orbit the Sun. Since the question focuses on objects not exceeding a meter, meteoroid is the appropriate term.