standard acceleration

The acceleration imparted by the earth’s gravitation to a body located on the earth’s surface: If you raise such a body up a bit and let it fall, it will accelerate 9.81 metres per second squared, in other words: in every second, its speed will increase by 9.81 metres per second.

Standard acceleration, abbreviated as g, is often used as a measure for accelerations. For instance, an acceleration of 2 g corresponds to 2·9.81=19.62 m/s².