startle

Etymology

From Middle English startlen, stertlen, stertyllen (“to rush, stumble along”), from Old English steartlian (“to kick with the foot, struggle, stumble”), equivalent to start + -le. Cognate with Old Norse stirtla (“to hobble, stagger”), Icelandic stirtla (“to straighten up, erect”). Compare also Middle English stertil (“hasty”). More at start.

verb

1. (intransitive) To move suddenly, or be excited, on feeling alarm; to start.
   a horse that startles easily
2. (transitive) To excite by sudden alarm, surprise, or apprehension; to frighten suddenly and not seriously; to alarm; to surprise.
   The high voice in the night air startled me. Without thinking, I started to run. Then stopped. I spun around, my heart heaving against my chest. And saw a boy. About my age. 1997, R. L. Stine, Say Cheese and Die, Again!
3. (transitive, obsolete) To deter; to cause to deviate.
   it would blast all their hopes, and startle all other princes from joining 1660, Edward Hyde, 1st Earl of Clarendon, The Life of Edward Earl of Clarendon, Lord High Chancellor of England
   As they turned into Hertford Street they startled a robin from the poet's head on a barren fountain, and he fled away with a cameo note. 1922, Michael Arlen, “Ep./4/2”, in “Piracy”: A Romantic Chronicle of These Days

noun

1. A sudden motion or shock caused by an unexpected alarm, surprise, or apprehension of danger.
   The figure of a man heaving in sight amidst these wide solitudes, always causes a startle and thrill of expectation and doubt, similar to the feeling produced by the announcement of " a strange sail ahead" on shipboard, during a long voyage. 1845, George Hooker Colton, James Davenport Whelpley, chapter 1, in The American review