Startled means jolted by something sudden. The half-second before you realise it was only the cat.
The word describes a state and, above all, a face: a startled expression, a startled look, startled eyes. It is used constantly of animals, since a startled horse or a startled bird is a real and dangerous thing. It is milder than frightened and much briefer, because being startled lasts a moment and then passes. English pairs it neatly with the sound that caused it, as in startled by the bang.
1adjectivestartledSuddenly surprised or frightened for a moment.
“She gave a startled cry.”