Automatic processing refers to thinking that is nonconscious, unintentional, involuntary, and effortless.
Automatic processing is what Psychologists call processing of information that guides behavior, but without conscious awareness, and without interfering with other conscious activity that may be going on at the same time: for example, driving slowly down a street (automatic processing) while looking for a specific address (conscious processing)
Moreover, Automatic processing refers to "implicit" or intuitive thinking that is effortless, habitual, and without awareness.
Other definition:
Automatic Processing is the the carrying out of a cognitive task with minimal resources. Typically, automatic processing occurs without intention, interferes minimally with other cognitive tasks, and may not involve conscious awareness.