Geometric term for a solid with a polygonal base and a point (apex). 錐体 (すいたい) is a common compound for 'cone' or 'pyramid' in medical and mathematical contexts.
In math class, we learned the formula for the volume of a cone/pyramid.
この立体は底面が四角形の錐です。
This solid is a pyramid with a quadrilateral base.
cone
square drill · regular pyramid
setting a drill bit; standing an awl
test boring; trial drilling
The kanji 錐 originally meant 'awl' or 'drill', but in modern Japanese it is used in geometry for a cone or pyramid, likely from the shape of a pointed tool. The reading すい is the on'yomi.