Plain English Meaning

Slip and skid are two ways an airplane can be out of balance in a turn. In a slip, the airplane is leaning into the turn too much and slides inward. In a skid, it isn't leaning enough and slides outward. The little ball on the instrument panel shows which one is happening.

Full Definition

An uncoordinated flight condition in which the airplane's lateral motion is not aligned with its longitudinal axis. In a slip, the airplane is banked more than the rate of turn requires, causing it to slide toward the inside of the turn. In a skid, the airplane is banked less than the rate of turn requires, causing it to slide toward the outside of the turn. The slip/skid indicator (the ball in the turn coordinator or inclinometer) shows this condition: the ball moves toward the slip side or the skid side of center.

Context Anchor

Seen during checks and in when checking the ball in the turn coordinator or similar .