Synonyms for Instant:

adj.

all (adjective)
instantaneous.
burning (adjective)
crying.
contemporary (adjective)
today, now.
instant (adjective)
exigent, instantaneous, on-the-spot, fast, prompt, present, clamant, insistent, imperative.

n.

promptly, suddenly, right now, straight away, headlong, straight. big, bout, a bit, short-term, time, twinkle, JIFF, tick. crisp, chilled, cool, point, cream, buttery, caramelized, chewy, calorific, crispy. bit (noun)
moment.
chance (noun)
occasion.
circumstance (noun)
conjuncture, happening, episode, milestone, status, condition, incidence, moment, event, situation, cardinal point, landmark, occasion, circumstance, basis, occurrence, juncture.
immediate (noun)
on-the-spot, ready-to-eat, premixed, precooked, ready-to-use, ready-to-serve, immediate, prompt, prepared.
instant (noun)
exigent, clamant, twinkling, fast, occasion, trice, blink of an eye, second, moment, wink, jiffy, minute, tick, split second, point, inst, flash, present, crying, juncture, instantaneous, imperative, insistent, time, new york minute.
now (noun)
today, now, present, here and now, immediacy.
split second (noun)
blink of an eye.
timelessness (noun)
timelessness, instantaneousness.
without delay (noun)
first off, right away, forthwith, time, right off, instantly, straightaway, straight off, at once, directly, immediately.

Other synonyms:

New York minute
new york minute.
JIFF. time, short-term. bout. tick. point. ready
prepared.
without delay
forthwith, right away, straight off, immediate, right off, straightaway, directly, instantly, immediately.

Usage examples for instant

  1. But the doctor was the doctor an instant longer. – The Crime Doctor by Ernest William Hornung
  2. For an instant only. – Memoirs of Sherlock Holmes by Sir Arthur Conan Doyle
  3. She doesn't want the fish to miss the water for an instant – The Social Cancer A Complete English Version of Noli Me Tangere by José Rizal