Slang: jumpy

finition: Nervous or apprehensive; afraid that something bad will happen.
Example: 1) I'm always a little bit jumpy when I walk by the graveyard at night.

2) Rachel sure is jumpy today. I said 'hello' and she nearly hit the ceiling!
Etymology: To 'jump' means to move into the air by springing or leaping up, so someone who is 'jumpy' is on the edge of leaping into the air in surprise or fear.

Synonyms: jittery