1. An ancient timekeeping device that measures time by the regulated flow of water from one container to another.
Usage: Also called a water clock.; Used in ancient Egypt, Greece, China, and the Middle East.; Historical or technical context.

Examples

• The ancient Egyptians used a clepsydra to measure the passage of time during the night.
• A clepsydra operates on the principle that water flows at a constant rate from a higher vessel to a lower one.
• Before mechanical clocks were invented, the clepsydra was one of the most reliable timekeeping devices.
• Archaeologists discovered a bronze clepsydra in the ruins of a Roman temple.
• The clepsydra marked the hours as water dripped steadily through a small opening.