Synonyms of instantaneous
- 1 Syllable
- prompt, quick, fast
- 2 Syllables
- presto, direct, quickest, quicker, instant, asap, rapid, prompter
- 3 Syllables
- on-the-spot, spontaneous, split-second, hair-trigger
- 4 Syllables
- unlooked-for, momentary, transitory, harefooted, unexpected