GNO'MON, n. no'mon. [Gr. an index, to know.]

1. In dialling, the style or pin, which by its shadow shows the hour of the day. It represents the axis of the earth.

2. In astronomy, a style erected perpendicular to the horizon, in order to find the altitude of the sun.

3. The gnomon of a globe, is the index of the hour-circle.