|the offspring of a zebra and a donkey.|
|an arrangement of five objects, as trees, in a square or rectangle, one at each corner and one in the middle.|
|acceleration (āk-sěl'ə-rā'shən) Pronunciation Key
The rate of change of the velocity of a moving body. An increase in the magnitude of the velocity of a moving body (an increase in speed) is called a positive acceleration; a decrease in speed is called a negative acceleration. Acceleration, like velocity, is a vector quantity, so any change in the direction of a moving body is also an acceleration. A moving body that follows a curved path, even when its speed remains constant, is undergoing acceleration. See more at gravity, relativity.