crash dive

Short definition from Wiktionary

Noun

1. 1
   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.
2. 2
   A rapid descent by a person or thing, ending in a violent collision.
3. 3
   Three quarters of a front somersault, beginning on the feet and landing on the back.
4. 4
   Alternative form of crash dive.

Verb

1. 1
   To perform a crash dive.
2. 2
   To cause (a submarine) to perform a crash dive.
3. 3
   To rapidly descend, intentionally or accidentally, in a manner that ends in a violent collision.
4. 4
   To rapidly descend, in a manner that ends in a violent collision with (something).
5. 5
   To cause (something) to descend rapidly, in a manner that ends in a violent collision.
6. 6
   Alternative form of crash dive.