Plain English Meaning
Looking at your instruments in a steady, repeating pattern so you always know what the airplane is doing, instead of staring at just one gauge.
Full Definition
The continuous, systematic scanning of flight instruments by a pilot to monitor aircraft performance, detect changes, and verify that the aircraft is doing what is intended. It involves moving the eyes between instruments in a deliberate pattern rather than fixating on any single one.
Context Anchor
Used in instrument flying instruction and habit-pattern training, especially when the pilot must control the airplane mainly by looking at instruments instead of the outside view.