Synonyms of instantaneous in English:

instantaneous


See definition of instantaneous

adjective

1‘it may be difficult for you to make an instantaneous response to what is said’

SYNONYMS
immediate, instant, on-the-spot, prompt, direct, swift, speedy, rapid, quick, expeditious, express, lightning
sudden, hurried, hasty, precipitate, abrupt
informal snappy, p.d.q., pretty damn quick
literary fleet, rathe
rare alacritous
ANTONYMS

delayed, long-term