What is Gnetophyte?

Gnetophyte definition and meaning on Dictionary terms:
the raised part of a sundial that casts the shadow; a style.
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.
Geometry. (formerly) the part of a parallelogram that remains after a similar parallelogram has been taken away from one of its corners.