noun-modifying (irregular)
Describes something that happens or is done in an instant; often used in compound nouns like 瞬発力 (instantaneous power) or 瞬発的な (instantaneous).
He excels in instantaneous power.
An instantaneous decision is required.
explosive power; instantaneous force · quick responsiveness; instantaneity
Compound of 瞬 (instant) and 発 (emit, occur). The exact historical derivation is uncertain, but it is a relatively modern coinage.