1. Immediate
2. Prompt
3. Rapid
4. Quick
5. Swift
6. Accelerated
7. Expeditious
8. Breakneck
9. Speedy
10. Express
11. Hurried
12. Hasty
13. Breakneck
14. Precarious
15. Lightning
16. Flash
17. Snap
18. Brisk
19. Instant
20. Spontaneous
21. Abrupt
22. Fleeting
23. Blinking
24. Momentary
25. Precipitate
26. Sudden
27. Precipitous
28. Excessive
29. Overhasty
30. Unforeseen

If you’re looking for the best ideas for synonyms for the word «instantaneous,» you’ve come to the right place. There are many other words for instantaneous, such as immediate, prompt, rapid, quick, swift, accelerated, expeditious, breakneck, speedy, express, hurried, hasty, precarious, lightning, flash, snap, brisk, instant, spontaneous, abrupt, fleeting, blinking, momentary, precipitate, sudden, precipitous, excessive, overhasty, and unforeseen. Each of these words can be used to describe something that is happening or has happened very quickly. No matter what word you choose, you can be sure to convey the same meaning — that something happened immediately and without delay.