Klick is a common military term meaning kilometer when referring to distance. Its use became popular among US soldiers in Vietnam during the 1960s, although veterans of the war recall its usage as early as the 1950s. The term is of unknown origin. It is likely to be an example of condensed pronunciation or contraction of the term kilometer, although other theories exist.
Either a kilometre or a kilometre per hour ("kilometer" for Americans) depending on context. Pronounced as "click" but always written with an initial 'k'.
Common in Canada. In the US it's strongly associated with the military.
See k which can also be used for "kilometre" but not for "kilometre per hour".
"It's about two klicks up the road." (Distance: 2 km)
"We were doing ninety klicks." (Speed: 90 km/hr)
The use of the word "blue" to refer to sexually explicit content was first recorded in Scotland in 1824. "Blue" meant "lewd" because prostitutes dressed in blue gowns.