Posthaste

Part of speech: adverb

Pronunciation: /ˌpəʊstˈheɪst/

Definitions

1. With great speed or urgency, done immediately and without delay
2. With utmost speed and without any delay or hesitation
3. Done or performed with maximum swiftness and immediate action

Etymology: "Posthaste" began as a set of instructions written on letters. Messengers carrying mail by horse relay were told to hurry with the words "haste, post, haste," meaning the letter should travel quickly and be passed along the post without delay. Over time, people stopped reading the phrase as a three-part command and reinterpreted it as a single compound: "post" plus "haste," a fast delivery by post. That reinterpretation changed the word's function. What had been an urgent note on an envelope became an adverb meaning with utmost speed, and the sense of the postal system itself faded from view. The word now describes almost any action carried out without hesitation, even when no letter or horse is involved.

Synonyms: immediately, instantly, hastily, promptly, swiftly

Antonyms: slowly, leisurely, gradually, deliberately, carefully