Yes, the sentence "I was utterly surprised" is grammatically correct. It means that the speaker was completely or intensely surprised by something. The word "utterly" emphasizes the level of surprise.
Here are a few possible rephrasings:
- I was completely surprised.
- I was totally taken aback.
- I was extremely surprised.
- I was absolutely astonished.
Each of these alternatives conveys a similar meaning, but with slight variations in tone