Definition of startle reflex in English:

startle reflex

Pronunciation /ˈstɑːtl ˌriːflɛks/


  • An involuntary reaction to a sudden stimulus, especially a loud noise, often involving contraction of groups of muscles of the limbs and neck; a similar reaction shown by an animal.

    In human infants this reaction is also called the Moro reflex and is characterized by distinctive movements of the arms and legs.


Early 20th century; earliest use found in Military Surgeon. From startle + reflex.