Automatic (adjective)

1. Done or operating in a mechanical or unconscious way, as if by habit or reflex.
2. Self-acting or self-regulating.

Origin:

Late 18th century: from french automatique, or via late latin from greek automatikos "self-acting", from autos "self" + -matos "doing", from matos "mad, foolish".

Examples:

1. The car has an automatic transmission.
2. He opened the door with an automatic gesture.
3. The process is now fully automatic.
4. She had an automatic response to his question.
5. The camera has an automatic focus.