Definition of "klick"

Several klicks closer, the ruins of the City of Poets rose jaggedly against the skyline.

1990, Dan Simmons, The Fall of Hyperion, 1st edition, New York: Doubleday, page 165

an asteroid between one and three kilometers wide had slammed into the ground at fifteen klicks per second.

2002, Robert J. Sawyer, Hominids

Chief, can you hear me?...(static) My bird's down. Half a klick -(static)- downriver from your position.

2007 September 25, Bungie, Halo 3, v1.0, Microsoft Game Studios, Xbox 360, level/area: Sierra 117