noun
water clock; clepsydra
A timekeeping device that measures time by the regulated flow of water. Often used in historical or technical contexts.
古代エジプトでは水時計が使われていた。
Water clocks were used in ancient Egypt.
砂時計 is an hourglass using sand, whereas 水時計 uses water.
Compound of 水 (water) and 時計 (clock). The reading みずどけい follows rendaku voicing of とけい to どけい.