instantly

As adverbs the difference between instantly and continuously

is that instantly is urgently; with insistence while continuously is without pause.

As adverbs the difference between incessantly and instantly

is that incessantly is in a manner without pause or stop, especially to the point of annoyance; not ceasing while instantly is urgently; with insistence.

As adverbs the difference between readily and instantly

is that readily is without unwillingness or hesitation; showing readiness while instantly is urgently; with insistence.

As adverbs the difference between summarily and instantly

is that summarily is (manner) in a summary manner while instantly is (archaic) urgently; with insistence.

As adverbs the difference between once and instantly

is that once is before while instantly is (archaic) urgently; with insistence.

As a noun once

is before.

As adverbs the difference between presently and instantly

is that presently is while instantly is (archaic) urgently; with insistence.

As adverbs the difference between rapidly and instantly

is that rapidly is with speed; in a rapid manner while instantly is (archaic) urgently; with insistence.

As adverbs the difference between instantly and momentarily

is that instantly is (archaic) urgently; with insistence while momentarily is in a momentary manner; for a moment or instant.

As adverbs the difference between instantly and effortlessly

is that instantly is urgently; with insistence while effortlessly is without effort; without difficulty or struggle.

Instantly is a synonym of at_once.

As adverbs the difference between instantly and at_once

is that instantly is (archaic) urgently; with insistence while at_once is (obsolete) in one group; together.