Frequency: The word is one of the 3000 most common words in English.
1.
If you are ~ at something, you have a feeling of surprise, because it is unexpected or unusual.
This lady was genuinely ~ at what happened to her pet...
Chang seemed ~ to find the big living-room empty...
ADJ: usu v-link ADJ, oft ADJ at/by n, ADJ to-inf, ADJ that/how
2.
see also surprise