Acceleration is the speeding-up or slowing-down of an object.  Newton's 2nd law of motion states that when a force is applied to an object it either slows-down, speeds-up or changes direction.  Acceleration, thus, has direction associated with it.  When you apply a force to an object the object is accelerated in same direction as the force applied.

Accelerate: to apply a force to an object to make it slow-down, speed-up or change direction.

 

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