double-nickel

Etymology
From trucker slang in the 1970s referring to the national 55 mph speed limit, based on.

Noun

 * 1)  The national speed limit of 55 miles per hour introduced in the USA in 1974.
 * 2)  The number 55 (by extension).
 * 1)  The number 55 (by extension).
 * 1)  The number 55 (by extension).

Verb

 * 1)  To travel at 55 miles per hour.