adverb: with all possible speed
“You must leave posthaste,” Virginia theatrically admonished her guests, “or you’ll miss your ferry!”
“Yes, West Palm Beach commissioners should green-light the chief’s efforts to address the issue posthaste.” — Palm Beach Post, September 3, 2014
Did you know?
In the 16th century, the phrase “haste, post, haste” was used to inform “posts,” as couriers were then called, that a letter was urgent and must be hastily delivered. Posts would then speedily gallop along a route, with a series of places at which to get a fresh horse or to relay the letter to a fresh messenger. Shakespeare was one of the first to use a version of the phrase adverbially in Richard II. “Old John of Gaunt … hath sent post haste / To entreat your Majesty to visit him,” the Bard versified. He also used the phrase as an adjective (a use that is now obsolete) in Othello: “The Duke … requires your haste-post-haste appearance,” Lieutenant Cassio reports to the play’s namesake. Today, the word still possesses a literary flair attributable to the Bard.