startle
     n : a sudden involuntary movement; "he awoke with a start" [syn:
          {jump}, {start}]
     v 1: to stimulate to action ; "..startled him awake"; "galvanized
          into action" [syn: {galvanize}, {galvanise}]
     2: move or jump suddenly, as if in surprise or alarm; "She
        startled when I walked into the room" [syn: {jump}, {start}]
Source: WordNet® 2.0