noun
hourglass; sandglass
A device for measuring time by the flow of sand from one glass bulb to another.
砂時計の砂が全部落ちるまで、じっと待っていた。
I waited quietly until all the sand in the hourglass had fallen.
Compound of 砂 (すな, 'sand') and 時計 (とけい, 'clock'). The reading すなどけい is a regular rendaku form.