Plain English Meaning
The fastest speed at which you can yank the controls all the way over without breaking the aircraft. Below this speed, the wings will stop flying (stall) before anything bends.
Full Definition
The maximum speed at which full or abrupt control inputs can be applied without overstressing the airframe. At or below Va, the wing will stall before the structure reaches its design load limit, protecting the aircraft from damage caused by sudden control movement or strong gusts. Va decreases as aircraft weight decreases.
Context Anchor
Seen in the aircraft’s operating handbook, on airspeed markings or placards when provided, and in training discussions about , , and .