runaway

Short definition from Wiktionary

Noun

1. 1
   A person or animal that runs away or has run away; a person, animal, or organization that escapes captivity or restrictions.
2. 2
   A vehicle (especially, a train) that is out of control.
3. 3
   An object or process that is out of control or out of equilibrium.
4. 4
   The act of running away, especially of a horse or teams.
5. 5
   An overwhelming victory.

Adjective

1. 1
   Having run away; escaped; fugitive.
2. 2
   Having run away; escaped; fugitive: Having escaped from the control of the rider or driver.
3. 3
   Having run away; escaped; fugitive: Pertaining to or accomplished by running away or eloping.
4. 4
   Easily won, as a contest.
5. 5
   Accelerating out of control.
6. 6
   Unchecked; rampant.
7. 7
   Deserting or revolting against one's group, duties, expected conduct, or the like, especially to establish or join a rival group, change one's life drastically, etc.