Plain English Meaning
It is your body's built-in sense of how it is moving and where it is in space, without having to look. In an airplane, it is what lets you feel a turn, a climb, or a bump through your seat and the controls.
Full Definition
The body's sense of the position, motion, and force of its own parts, received through nerve endings in muscles, tendons, and joints. In flying, it is the pilot's awareness of the airplane's movement and attitude through the physical pressures and motions felt in the seat, controls, and body.
Context Anchor
Seen in the Airplane Flying Handbook section on the feel of the airplane, where pilots learn how body sensations and control pressures help them handle the aircraft smoothly.
Derivation
From Latin proprius meaning 'one's own' and capere meaning 'to take or grasp.' Literally, 'sensing one's own.' This helps the pilot meaning click: it is the sense that picks up your own body's position and movement, including how the airplane is pushing on you.