Plain English Meaning
A wing that gets narrower from front to back as it goes out toward the tip, so the tip is a smaller wing section than the part attached to the fuselage.
Full Definition
A wing whose chord (the distance from leading edge to trailing edge) decreases progressively from the wing root at the fuselage to the wing tip. The leading edge, trailing edge, or both may be angled to produce the taper.
Context Anchor
Seen in visual maneuver discussions, including eights on pylons, where the pilot uses the wing and outside references to judge position.