Which term refers to the opposite of 'wind'?

The term that refers to the opposite of 'wind' is 'unwind.' In this context, 'wind' can mean to twist or coil something, such as winding yarn around a spool. Therefore, 'unwind' signifies the action of reversing that process—loosing or straightening out something that has been wound up. This makes 'unwind' the correct choice, as it directly indicates the opposite action of winding. The other terms do not convey this concept of reversal related to winding.