Plain English Meaning
The automatic body-and-mind jolt you get when something happens out of nowhere. For a moment you freeze up, your heart races, and your thinking briefly stalls before you can react.
Full Definition
An involuntary, reflexive physical and mental reaction to a sudden, unexpected event, typically lasting only a few seconds, characterized by a brief freeze, elevated heart rate, muscle tensing, and a temporary disruption of attention and cognitive processing.
Context Anchor
Seen in human factors discussions about surprise, emergencies, and how pilots react when something suddenly does not match what they expected.
Derivation
From Middle English 'stertlen' meaning to rush or move suddenly. The word captures the involuntary nature of the reaction — it happens to you before you can choose it.