Emily Dickinson Lexicon

GNO'MON, n. [no'mon; Gr. γνωμων, an index, from the root of γινωσκω, to know.]

1. In dialing, the style or pin, which by its shadow shows the hour of the day. It represents the axis of the earth. Encyc.
2. In astronomy, a style erected perpendicularly to the horizon, in order to find the altitude of the sun. Encyc.
3. The gnomon of a globe, is the index of the hour-circle. Encyc.