Plain English Meaning
How fast you are flying compared to how many Gs the airplane is feeling. The two are linked: at low speeds the wing stalls before it can pull many Gs, and at high speeds the wing can pull enough Gs to bend or break the airplane.
Full Definition
The relationship between an aircraft's airspeed and the load factor (G-force) it experiences or can safely sustain. This relationship is plotted on a Vg diagram (velocity-G diagram), which shows the airspeed range within which the aircraft can be flown without exceeding structural limits or aerodynamic stall.
Context Anchor
Seen when reading the Vg diagram in load factor discussions, especially when learning how and affect the airplane’s structural limits.