Synonyms for Posthaste:

• adj.

  •fast (adjective)
  • like crazy,
  • flashing,
  • like a bat out of hell,
  • double-time,
  • like all get out,
  • hypersonic,
  • hairtrigger,
  • in nothing flat,
  • velocious,
  • like mad,
  • speedball,
  • post-haste,
  • snapper,
  • in a jiffy,
  • screamin',
  • Expeditive,
  • BLUE STREAK.
  •quick (adjective)
  • ex-press,
  • most harefooted,
  • lead out,
  • more harefooted,
  • ex press.

• adv

  •fast (adverb)
  • in haste,
  • like a shot,
  • like wildfire,
  • like a flash,
  • like greased lightning,
  • in short order.
  •hastily (adverb)
  • thoughtlessly,
  • on spur of moment,
  • heedlessly,
  • agilely,
  • on spur of the moment,
  • too quickly,
  • Subito,
  • Unpremeditatedly.
  •pell-mell (adverb)
  • Pellmell,
  • precipitiously,
  • Incontinently.
  •soon (adverb)
  • in time,
  • coming down the pike,
  • in a little while,
  • in a second,
  • in due time,
  • in a minute,
  • by and by,
  • in a short time,
  • before long,
  • any minute now.

• adv.

  •fast (adverb)
  • hurriedly,
  • straightaway,
  • directly,
  • fleetly.
  •hastily (adverb)
  • precipitately.
  •promptly (adverb)
  • un hesitatingly,
  • un-hesitatingly,
  • on dot.
  •rapidly (adverb)
  • in hurry,
  • in rush.
  •soon (adverb)
  • soonest,
  • ere long.

• Other synonyms:

  •
  • Lickety Split,
  • pronto.
  •
  • flat out.
  •Other relevant words:
  • clever,
  • sharply,
  • eagerly,
  • Lickety Cut,
  • precipitously,
  • by forced marches,
  • against the clock,
  • explicitly,
  • cursory,
  • early,
  • Fastly,
  • agile,
  • on-the-spot,
  • bright,
  • dexterous,
  • cursorily,
  • presto,
  • Tantivy,
  • instant,
  • earnestly,
  • keen,
  • readily,
  • suddenly,
  • instantaneously,
  • like a house on fire,
  • like a blue streak,
  • without delay,
  • keenly,
  • intelligent,
  • like a streak,
  • specially,
  • shortly,
  • like the wind,
  • briskly,
  • alert,
  • hell-for-leather,
  • alive,
  • at short notice,
  • at full tilt,
  • instantly,
  • all at once,
  • at full speed,
  • immediately,
  • abrupt,
  • straight,
  • active,
  • abruptly,
  • in a flash,
  • hurried,
  • immediate,
  • expressly.

Antonyms for Posthaste:

• adv.

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