MEANING: noun: Any of various hares having long ears and very long hind legs.
verb intr.: To move or begin to move very quickly.
adjective: Moving or beginning to move very quickly.

ETYMOLOGY: A combination of jackass + rabbit. Earliest documented use: 1863, in a figurative use: 1922.

NOTES: The word jackrabbit is a misnomer. A jackrabbit is a hare, not a rabbit. It is called a jackrabbit because of its long ears, as if those of a jackass. The metaphorical use is from a jackrabbit’s sudden movement. This has given us the slang “jackrabbit start” meaning a start in which a person accelerates very quickly as a traffic light turns green, maybe even before the light has turned. Like most animal-related metaphors, this unfairly maligns our furry friends. There have been no reported sightings of jackrabbits jumping a red light.

JACK, RABBI - John, meet my spiritual advisor

PACK RABBIT - a leveret capable of carrying large loads

JA, CRAB BIT - Were you able to trap that crustacean, Hans?