Solid, naturally occurring aggregates of minerals or mineraloids.

Here's why:

* Solid: Rocks are not liquids or gases. They have a definite shape and volume.

* Naturally Occurring: Rocks are formed by natural processes, not manufactured.

* Aggregates: Rocks are made up of multiple mineral grains that are stuck together.

* Minerals or Mineraloids: Minerals are naturally occurring, inorganic solids with a specific chemical composition and crystalline structure. Mineraloids are similar to minerals but don't have a definite crystalline structure.

This phrase covers the essential characteristics of rocks and is both accurate and concise.