n. 1 the rod or pin etc. on a sundial that shows the time by the position of its shadow. 2 Geom. the part of a parallelogram left when a similar parallelogram has been taken from its corner. 3 Astron. a column etc. used in observing the sun's meridian altitude. gnomonic adj.
[ F or L gnomon f. Gk gnomon indicator etc. f. gignosko know ]