Synonyms for Posthaste:

• adj.

  •fast (adjective)
  • fleet,
  • rapidly,
  • in nothing flat,
  • chop-chop,
  • Lickety Split,
  • like a bat out of hell.

• adv.

  •fast (adverb)
  • at once,
  • breakneck,
  • directly,
  • expeditious,
  • expeditiously,
  • fleet,
  • fleetly,
  • hastily,
  • hasty,
  • headlong,
  • hurriedly,
  • pell-mell,
  • promptly,
  • pronto,
  • quick,
  • quickly,
  • rapid,
  • rapidly,
  • speedily,
  • speedy,
  • straightaway,
  • swift,
  • swiftly,
  • full tilt,
  • double-quick.
  •hastily (adverb)
  • hastily,
  • precipitately,
  • speedily.

• adv

  •fast (adverb)
  • fleetly,
  • in haste,
  • like a shot,
  • full tilt,
  • like wildfire,
  • like a flash,
  • like greased lightning.
  •hastily (adverb)
  • double-quick.
  •very fast (adverb)
  • swiftly.

• Other synonyms:

  •
  • apace,
  • Lickety Split,
  • pronto.
  •
  • flat out,
  • quick,
  • quickly.
  •
  • fast.
  •Other relevant words:
  • abrupt,
  • abruptly,
  • active,
  • against the clock,
  • agile,
  • alert,
  • alive,
  • all at once,
  • amain,
  • apace,
  • at full speed,
  • at once,
  • breakneck,
  • bright,
  • briskly,
  • chop-chop,
  • clever,
  • cursorily,
  • cursory,
  • dexterous,
  • directly,
  • eagerly,
  • early,
  • earnestly,
  • expeditious,
  • expeditiously,
  • explicitly,
  • express,
  • expressly,
  • fast,
  • flat out,
  • fleet,
  • fleetly,
  • hastily,
  • hasty,
  • headlong,
  • hell-bent,
  • hot,
  • hurried,
  • hurriedly,
  • immediate,
  • immediately,
  • in a flash,
  • in haste,
  • instant,
  • instantaneously,
  • instantly,
  • intelligent,
  • keen,
  • keenly,
  • Lickety Cut,
  • Lickety Split,
  • nimble,
  • on-the-spot,
  • pell-mell,
  • post,
  • precipitately,
  • precipitously,
  • presto,
  • prompt,
  • promptly,
  • pronto,
  • quick,
  • quickly,
  • rapid,
  • rapidly,
  • readily,
  • sharply,
  • shortly,
  • soon,
  • specially,
  • speedily,
  • speedy,
  • straight,
  • straightaway,
  • suddenly,
  • swift,
  • swiftly,
  • trippingly,
  • without delay,
  • Fastly,
  • Tantivy,
  • like a shot,
  • hell-for-leather,
  • snappily,
  • full tilt,
  • at full tilt,
  • on the double,
  • at short notice,
  • like wildfire,
  • in nothing flat,
  • like a bat out of hell,
  • like a blue streak,
  • like a flash,
  • like a house on fire,
  • like a streak,
  • like greased lightning,
  • like the wind,
  • double-quick,
  • in double time,
  • in high gear.

Antonyms for Posthaste:

• adv.

  • Other antonyms:
    belatedly, deliberately, leisurely, lingeringly, ploddingly, slow, slowly, sluggishly, tardily, laggardly.