Speed is a way of measuring how quickly something is moving or being done, or something moving fast.

something that does not or cannot change or vary.8.Physics. a number expressing a property, quantity, or relation thatremains unchanged under specified conditions.

  1. able to be changed or adapted."the drill has variable speed"
  1. 1.an element, feature, or factor that is liable to vary or change.

a quantity, rating, or the like that represents or approximates anarithmetic mean:

a scalar measure of the rate of movement of a body expressed as the rate of change of position with respect to time at a particular point. It is measured in metres per second, miles per hour, etc