What characteristic defines a 'swept wing' design?

A swept wing design is characterized by wings that are angled backward relative to the aircraft's fuselage. This design is commonly used in high-speed aircraft because it helps to delay the onset of airflow separation and reduces drag at high speeds. By angling the wings back, the aerodynamic efficiency is improved, allowing the aircraft to achieve better performance in terms of speed and fuel efficiency.

Swept wings are particularly beneficial in subsonic and transonic flight where they help maintain stability and control when approaching the sound barrier. The shape also alters the lift distribution across the wing, contributing to better handling characteristics at high speeds.

This differs from straight wings, which extend directly out from the fuselage and are more common on slower aircraft. Forward-angled wings and variable geometry wings have different aerodynamic purposes and are not characteristics of swept wings.