Which type of precision-guided munition homes in on energy reflected from the target by another source?

Semi-active precision-guided munitions rely on an external source to illuminate the target, allowing them to home in on the energy reflected from that target. In this type of guidance, the munition itself does not emit any energy but rather detects the reflected signals from the target, which is illuminated by a separate source, such as a laser designator or another targeting system. This method enables the munition to achieve a high degree of accuracy by using the reflected energy to guide its trajectory.

Active guidance munitions, on the other hand, can detect and home in on targets using their own radar or sensor systems. Passive guidance munitions detect the energy emitted by the target itself, such as infrared or radio frequency emissions, without needing an external source. Terminal guidance refers to the final phase of a munition's flight path, where it adjusts its trajectory for impact, often using radar or other systems.

Therefore, the defining characteristic of semi-active guidance is its dependence on reflected energy from an external source, making it the correct answer to the question.