mind boggling
/ˈmaɪndˌbɑɡlɪŋ/
adjective
- Extremely surprising, impressive, or difficult to imagine.
- The athlete's speed was mind-boggling; she broke the world record by two seconds.
- It's mind-boggling how fast technology has changed in the last twenty years.
- The amount of data stored on that tiny chip is mind-boggling.
Antonyms