What is meant by uniform acceleration

When an object undergoes uniform acceleration, its velocity changes by the same amount per unit of time.

For example, a person jumping off a cliff into a pool of water below undergoes a uniform acceleration of approximately 9.81m/s². This means that, for every second that passes, the person's downward velocity increases by 9.81m/s

Uniform acceleration basically means acceleration that is constant, the same speed or velocity the whole time. Nothing more to add really.