hourglass
n. B1 Intermediate US //ˈaʊɝˌɡɫæs// UK //ˈaʊəɡlɑːs// hour·glass
n. a glass container with two bulbs connected by a narrow neck. Sand flows from the top bulb to the bottom one, and it takes exactly one hour for all the sand to fall.
n. a glass vessel consisting of two bulbs connected by a narrow neck, containing sand that flows from the upper to the lower bulb at a constant rate. Used historically to measure time intervals.
The hourglass measures exactly one hour of time.
The old clockmaker used an hourglass to time the assembly of the delicate gears in the watch.
While modern quartz clocks offer superior precision, the hourglass remains a powerful symbol of the passage of time and the inevitability of its end.
From hour + glass.