any of various large hares of western North America, having very long hind legs and long ears.
jack•rab•bitPronunciation: ( jak'rab"it), [key]
resembling a jack rabbit, as in suddenness or rapidity of movement: The car made a jackrabbit start when the traffic light turned green.
to go or start forward with a rapid, sudden movement.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.