/noh"mon/ , n.
1. the raised part of a sundial that casts the shadow; a style. See illus. under sundial .
2. an early astronomical instrument consisting of a vertical shaft, column, or the like, for determining the altitude of the sun or the latitude of a position by measuring the length of its shadow cast at noon.
3. Geom. (formerly) the part of a parallelogram that remains after a similar parallelogram has been taken away from one of its corners.
[ 1540-50; gnomon pin of a sundial gnómon lit., interpreter, discerner ]