au·to·mat·ic 
(ô′tə-mătĭk)
(ô′tə-mătĭk)adj.
1.
a. Acting or operating in a manner essentially independent of external influence or control: an automatic light switch; a budget deficit that triggered automatic spending cuts.
b. Self-regulating: an automatic washing machine.
2.
a. Acting or done without volition or conscious control; involuntary: automatic shrinking of the pupils of the eyes in strong light.
b. Acting or done as if by machine; mechanical: an automatic reply to a familiar question.
3.
a. Capable of firing continuously until ammunition is exhausted or the trigger is released: an automatic rifle.
b. Semiautomatic: an automatic pistol.
n.
Idiom: 1. An automatic machine or device.
2.
a. An automatic firearm.
b. A semiautomatic firearm.
3. A transmission or a motor vehicle with an automatic gear-shifting mechanism.
4. Football See audible.
on automatic
Functioning by or as if by automatic machine or device.
[From Greek automatos : auto-, auto- + -matos, willing; see men-1 in the Appendix of Indo-European roots.]
au′to·mati·cal·ly adv.
au′to·ma·tici·ty (-mə-tĭsĭ-tē) n.