A helmet worn by motorcyclists worn to protect the head in case of an accident.

(automotive, informal) A transmission with a sliding mesh, used in older vehicles; gear changes are often accompanied by loud noises.

A cymbal that produces a loud, sharp crash, used for occasional accents.

(UK, emergency medicine) crash cart

(informal, emergency medicine) A portable set of trays, drawers and shelves containing equipment and medication used in a medical emergency

(computing) A collision of the head of a hard drive with the platter, resulting in permanent damage to the hard drive.

The collision of one or more cars / (by extension) A mess or disaster, especially one that attracts a lot of attention.

plural of crash test

A test of crashworthiness, usually involving the controlled crashing of a vehicle with dummies in place of human passengers.

(idiomatic, military) An emergency maneuver by a submarine in which it suddenly descends, especially to considerable depth, usually in order to escape an attack or avoid a collision.