double-nickel

== English == === Etymology === From trucker slang in the 1970s referring to the national 55 mph speed limit, based on nickel (“five-cent coin”). === Noun === double-nickel (plural double-nickels) (US slang) The national speed limit of 55 miles per hour introduced in the USA in 1974. (US slang) The number 55 (by extension). === Verb === double-nickel (third-person singular simple present double-nickels, present participle (US) double-nickeling or (UK) double-nickelling, simple past and past participle (US) double-nickeled or (UK) double-nickelled) (with dummy it) To travel at 55 miles per hour.