Final answer:
The term 'darken ship' is a naval procedure to reduce the visibility of a ship by securing light-emitting fittings and hatches. The terms WILLIAM, Circle WILLIAM, DOG ZEBRA, and Circle ZEBRA do not correspond to commonly known procedures and seem to be specific codes or acronyms whose meanings are not provided in the question.
Step-by-step explanation:
The phrase "darken ship" in a naval context usually refers to the procedure carried out on a ship to minimize visible light and make it less visible to the enemy at night or during a period where concealment is necessary. This process often involves securing certain fittings and hatches to prevent light from escaping and making the ship more detectable. Such measures could include closing watertight doors, hatches, or securing blackout curtains over portholes and windows. It might also involve switching off or dimming non-essential lights.
The specific terms listed in the question, such as WILLIAM, Circle WILLIAM, DOG ZEBRA, and Circle ZEBRA, do not correspond to common naval terms related to the process of darkening a ship. In this context, they seem to be a set of code names or possibly acronyms that might refer to different sets of equipment or procedures within a particular navy or fleet, however, without more context, it is impossible to give an accurate answer as to what exactly each of these terms refers to.