Speeding up refers to when an object is increasing its velocity over time. In other words, if the magnitude of an object's acceleration is positive, it means that the object is speeding up.
Related terms
Deceleration: The negative acceleration that occurs when an object slows down or decreases its velocity.
Uniform Motion: When there is no change in velocity; either constant speed or at rest.
Position-Time Graph: A graph that shows how an object's position changes over time.