An instant is a very short time. In combinations like instant coffee and instant replay it means available right away without a wait.

Instant and moment mean the same thing if you are talking about a particular time in the past like you remember the instant or moment you realized that you had won the lottery. However, the two words are very different when talking about time in the future. "I'll be there in an instant" means you're coming as quickly as possible, whereas if you say "I'll be there in a moment," someone is going to have to wait a bit for you.

Definitions of instant

n a very short time (as the time it takes the eye to blink or the heart to beat)

New York minute, blink of an eye, flash, heartbeat, jiffy, split second, trice, twinkling, wink
Type of:
bit, minute, mo, moment, second
an indefinitely short time

n a particular point in time

minute, moment, second
show 9 types...
hide 9 types...
climax, culmination
the decisive moment in a novel or play
eleventh hour, last minute
the latest possible moment
moment of truth
a crucial moment on which much depends
moment of truth
the moment in a bullfight when the matador kills the bull
a very brief moment
a suitable moment
psychological moment
the most appropriate time for achieving a desired effect
high time
the latest possible moment
the time of a particular event
Type of:
point, point in time
an instant of time

adj occurring with no delay

instant gratification”
acting or moving or capable of acting or moving quickly

adj demanding attention

“an instant need”
clamant, crying, exigent, insistent
requiring attention or action

adj in or of the present month

temporal sense; intermediate between past and future; now existing or happening or in consideration

Sign up, it's free!

Whether you're a student, an educator, or a lifelong learner, can put you on the path to systematic vocabulary improvement.