as‧tound‧ed /əˈstaʊndəd, əˈstaʊndɪd/ adjective
very surprised or shocked Synonym : astonished
astounded by/at
She was astounded by his arrogance.

[TahlilGaran] Dictionary of Contemporary English ▲

surprised having the feeling you get when something happens that you did not expect:
I was surprised to see her again so soon.
I’m really surprised that he remembered my birthday.
Nobody was surprised when they split up.
a surprised expression
amazed [not before noun] extremely surprised, especially by something good or by something that seems hard to believe:
I’m amazed that he survived.
You’ll be amazed when you see the difference.
astonished extremely surprised:
He was astonished by how much she had changed.
an astonished look
astounded extremely surprised or shocked. Astounded sounds a little more formal and a little stronger than astonished:
She was astounded by how much it cost.
staggered/flabbergasted/dumbfounded [not before noun] extremely surprised or shocked:
‘What?’ I said, utterly staggered by his answer.
She just sat there looking flabbergasted.
stunned so surprised that you do not know what to do or say:
I was too stunned to protest.
Everyone seemed stunned by his outburst.
They listened in stunned silence.
speechless so surprised that you cannot speak:
I was speechless when I heard that I’d won.
taken aback [not before noun] surprised by what someone says or does, so that you are not sure how to react:
I was a little taken aback by her question.
Sharpe was somewhat taken aback by the girl 's directness.
nonplussed /nɒnˈplʌst $ nɑːn-/ formal surprised and a little confused:
She was nonplussed by such an odd question.
gobsmacked [not before noun] British English informal extremely surprised – a very informal use:
I was absolutely gobsmacked when they told me I had passed.

[TahlilGaran] English Thesaurus ▲