To surprise or frighten someone suddenly, making them jump or react in shock.
From Old English 'steortlian' meaning to kick or struggle; related to the idea of sudden physical movement. Over time it came to mean any sudden, involuntary response to surprise.
Your startle reflex is actually a survival mechanism left over from our evolutionary past—it's why we jump at sudden noises, helping our ancestors react quickly to threats!
Complete word intelligence in one call. Free tier — 50 lookups/day.