Synonyms for On-the-spot:

• adj.

  •extemporaneous/extemporary (adjective)
  • spur-of-the-moment,
  • off the cuff.
  •instant (adjective)
  • quick,
  • fast,
  • prompt.
  •snappy (adjective)
  • instant.
  •spur-of-the-moment (adjective)
  • spur-of-the-moment.

• adv.

  •here (adverb)
  • present.

• n.

  •
  • headlong,
  • suddenly,
  • promptly,
  • fast,
  • straight,
  • instantly.
  •on-the-spot (noun)
  • on-site,
  • on-the-scene.

• Other synonyms:

  •
  • suddenly,
  • PDQ,
  • summary,
  • already,
  • promptly,
  • directly,
  • Posthaste,
  • lightning,
  • instantly,
  • fast-paced,
  • summarily,
  • poof,
  • prompt.
  •
  • violently,
  • flash,
  • quick,
  • fast,
  • flat,
  • slap,
  • presto.
  •
  • here,
  • straight.
  •
  • present.
  •immediate
  • instant.
  •spontaneous
  • extemporaneous.
  •Other relevant words:
  • here,
  • present,
  • flash,
  • summarily,
  • summary,
  • suddenly,
  • straight,
  • already,
  • spur-of-the-moment,
  • instant,
  • connected,
  • poof,
  • slap,
  • violently,
  • PDQ,
  • snappy,
  • extemporaneous,
  • directly,
  • on,
  • flat,
  • lightning,
  • quick,
  • Posthaste,
  • fast-paced,
  • headlong,
  • promptly,
  • presto,
  • instantly,
  • fast,
  • prompt,
  • off the cuff.

Antonyms for On-the-spot:

• adj.

  • extemporaneous
    deliberate, premeditated.
  • extemporaneous/extemporary
    prepared, written, read, Rehearsed, planned.
  • instant
    late, future, old, unimportant, old-fashioned, past, delayed, slow, later, tardy, eventual.
  • present
    away, previous, far, absent, former, distant.
  • snappy
    nice, unfashionable, pleasant, happy, sluggish, outdated.

• adv.

  • here
    there.
  • Other antonyms:
    off-site.