GNO'MON, noun 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.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI