1
: extremely good
That meal was fantastic! [=excellent, terrific]
We had a fantastic [=great, wonderful] time!
2
: extremely high or great
The train runs at fantastic speeds.
3
also fantastical
: very strange, unusual, or unlikely
He concocted a fantastic [=wild, outlandish] scheme to rob the casino.
fantastic creatures
Cite this Entry
“Fantastic.” Merriam-Webster.com Simple Definition, Merriam-Webster, https://www.merriam-webster.com/simple/fantastic. Accessed 22 Jun. 2026.
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