To startle is to jump, like when you're surprised. If you’re sneaking through a dark room and step on a sleeping dog’s tail — you might startle the dog. If she barks, that dog startles you right back!

A startle is a quick, sharp movement, like a little jump that happens when you’re surprised or suddenly scared. If you sneak up on your mom and say "Boo!" you’ll startle her and she might jump up in her seat (before she yells at you to quit it). Alarm clocks and barking dogs often startle people. The original meaning of startle, around 1300, was "to run back and forth," from the Old English word styrtan, "to leap up."

Definitions of startle
  1. verb
    surprise greatly
    synonyms: ball over, blow out of the water, floor, shock, take aback
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    galvanise, galvanize
    to stimulate to action
    type of:
    cause to be surprised
  2. verb
    to stimulate to action
    “.. startled him awake”
    synonyms: galvanise, galvanize
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    type of:
    ball over, blow out of the water, floor, shock, take aback
    surprise greatly; knock someone's socks off
  3. verb
    move or jump suddenly, as if in surprise or alarm
    “She startled when I walked into the room”
    synonyms: jump, start
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    show 4 types...
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    start suddenly, as from fright
    startle with amazement or fear
    rear back
    start with anger or resentment or in protest
    go forward or start with a fast, sudden movement
    type of:
    move so as to change position, perform a nontranslational motion
  4. noun
    a sudden involuntary movement
    synonyms: jump, start
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    startle reaction, startle response
    a complicated involuntary reaction to a sudden unexpected stimulus (especially a loud noise); involves flexion of most skeletal muscles and a variety of visceral reactions
    Moro reflex, startle reflex
    a normal reflex of young infants; a sudden loud noise causes the child to stretch out the arms and flex the legs
    flinch, wince
    a reflex response to sudden pain
    type of:
    inborn reflex, innate reflex, instinctive reflex, physiological reaction, reflex, reflex action, reflex response, unconditioned reflex
    an automatic instinctive unlearned reaction to a stimulus
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