Source : Webster's Revised Unabridged Dictionary (1913)

Startle \Star"tle\, n.
   A sudden motion or shock caused by an unexpected alarm,
   surprise, or apprehension of danger.

         After having recovered from my first startle, I was
         very well pleased with the accident.     --Spectator.

Startle \Star"tle\, v. t. [imp. & p. p. {Startled}; p. pr. & vb.
   n. {Startling}.] [Freq. of start.]
   To move suddenly, or be excited, on feeling alarm; to start.

         Why shrinks the soul Back on herself, and startles at
         destruction?                             --Addison.

Startle \Star"tle\, v. t.
   1. To excite by sudden alarm, surprise, or apprehension; to
      frighten suddenly and not seriously; to alarm; to
      surprise.

            The supposition, at least, that angels do sometimes
            assume bodies need not startle us.    --Locke.

   2. To deter; to cause to deviate. [R.] --Clarendon.

   Syn: To start; shock; fright; frighten; alarm.

Source : WordNet®

startle
     n : a sudden involuntary movement; "he awoke with a start" [syn:
          {jump}, {start}]

startle
     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}]