The term pendulum hourglass refers to a type of timekeeping device, typically consisting of a weighted pendulum that swings from side to side inside an enclosure filled with sand. However, there are different words that can be used to refer to this type of device, depending on its precise design or function. For instance, an "hourglass" or "sandglass" may refer to any type of timer that uses sand to measure time, while a "pendulum clock" or "regulator clock" may specifically refer to a clock that uses a swinging pendulum to regulate its mechanics. Other synonyms for pendulum hourglass may include "gravity clock," "sands of time," "precision timer," or simply "timepiece".