hourglass

hourglass, glass instrument for measuring time, usually consisting of two bulbs united by a narrow neck. One bulb is filled with fine sand that runs through the neck into the other bulb in an hour's time. The date of its invention is unknown, but it was in use in ancient times. Similar devices for marking shorter periods of time, e.g., three-minute sandglasses for timing the cooking of eggs, are still used occasionally.

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An icon that is commonly used on graphical interfaces to mean "wait until finished." When the hourglass icon appears, you cannot do anything within that part of the application until that task has completed and the hourglass goes away.

An hourglass is a centuries-old device for counting time. It consists of two glass chambers attached to each other via a tiny opening. Half filled with sand, when the hourglass is turned over, the sand falls from one chamber to the other. The amount of sand and size of chambers and opening are precisely measured so that when all the sand from one side falls to the other, a certain amount of time has passed. See hourglassing.