Plain English Meaning
It's the point where you can do something well without having to think about each step. Your hands and eyes just do it, so your brain is free to handle other things.
Full Definition
The stage of skill learning at which a task can be performed correctly with little or no conscious thought, freeing the pilot's attention for higher-level decisions, situational awareness, and unexpected events.
Context Anchor
Seen in aviation training discussions about how student pilots move from slow, step-by-step performance to smooth, confident performance.
Derivation
From 'automatic,' which traces back to the Greek 'automatos,' meaning 'acting of itself.' The ending '-ity' turns it into a noun describing the of being automatic. In training, it captures the idea that the action now happens almost on its own.