Whet-stone, in natural history, a genus of vitreous stones, consisting of fragments of an indeterminate figure, sub opaque, and granulated.

Of this genus there are several species, some consisting of rougher, and others of smoother, or even of altogether impalpable particles; and used not only for whet-stones, but also for mill-stones, and other like purposes.

Cossecant, in geometry, the secant of an arch which is the complement of another to 90°. See Geometry.