Acceleration

Noun

1. The act of accelerating, or the state of being accelerated; increase of motion or action; as opposed to retardation or deceleration.

   "A falling body moves toward the earth with an acceleration of velocity."

2. The amount by which a speed or velocity increases (and so a scalar quantity or a vector quantity).

   "The boosters produce an acceleration of 20 metres per second per second."

3. The change of velocity with respect to time (can include deceleration or changing direction).
4. The advancement of students at a rate that places them ahead of where they would be in the regular school curriculum.