A more thorough explanation:

Allision (uh-lizh-uhn) is a term used in maritime law to describe when a moving vessel collides with a stationary object, such as an anchored ship or a pier. In the past, this term was used more frequently, but now the term collision is often used instead.

For example, if a ship is moving too quickly and crashes into a pier, this would be considered an allision. Another example would be if a boat collides with a stationary buoy in the water.

These examples illustrate the definition of allision because they both involve a moving vessel coming into contact with a stationary object, which is the key characteristic of an allision.