What is the correct term for the device that reduces voltage spikes caused by lightning?

The term that accurately describes a device designed to reduce voltage spikes caused by lightning is a lightning arrestor. These devices are specifically engineered to protect electrical equipment by diverting excess voltage to the ground when a lightning strike occurs or when there are other transient voltage surges. Essentially, they act as a safety mechanism, preventing damage to systems by ensuring that dangerous levels of voltage do not enter sensitive equipment.

While surge protectors also serve a similar purpose in protecting against voltage spikes, they are generally intended for more comprehensive use, often managing surges from various sources including power surges from utility sources. A voltage regulator maintains a steady voltage level but does not specifically address the potential explosive surges caused by lightning. Capacitors play a role in electrical systems but are not designed for protecting against voltage spikes. Hence, the lightning arrestor stands out as the most precise term for devices that deal specifically with the threats posed by lightning.