Which term describes the action of involuntarily recoiling or shrinking?

The term that describes the action of involuntarily recoiling or shrinking is "flinch." This word specifically captures the essence of a sudden, instinctive reaction to surprise or discomfort, often associated with a physical movement where a person draws back or tenses up. This reaction is typically quick and automatic, often in response to a perceived threat or shock, which aligns perfectly with the notion of recoiling.

In contrast, "winching" typically refers to the action of pulling something in or out using a winch, a mechanical device, rather than a bodily reflex. "Collapse" generally describes a falling down or breaking down of structure or health, which does not convey the idea of a quick, involuntary reaction. "Withdraw" implies a more conscious decision to retreat or move away from something, rather than the sudden reflexive action associated with flinching. Thus, flinch is the most accurate choice for describing involuntary recoiling or shrinking.