Plain English Meaning
The core flying skills every pilot must have: controlling the aircraft well, knowing where you are, making good decisions, talking on the radio properly, and following procedures the same way every time.
Full Definition
The fundamental piloting abilities required to safely operate an aircraft, including aircraft control by reference to outside visual cues and instruments, smooth and accurate use of the flight controls, sound judgment, situational awareness, navigation, communication, and consistent adherence to standard procedures and checklists.