1. The act or process of forming something or of taking form.

2. Something formed: beautiful cloud formations.

3. The manner or style in which something is formed; structure: the distinctive formation of the human eye.

4. A specified arrangement or deployment, as of aircraft, troops, or players on a sports team.

5. Geology A primary unit in the mapping of rock strata, consisting of a set of contemporaneous rocks having the same characteristics and origin.