noun
quadrangular pyramid
A pyramid with a quadrilateral base; a technical term in geometry.
四角錐の体積を求める公式を覚えていますか。
Do you remember the formula for finding the volume of a quadrangular pyramid?
四角柱 is a quadrangular prism, not a pyramid; it has two parallel quadrilateral bases.
Compound of 四角 (quadrilateral) and 錐 (pyramid, awl). The reading すい for 錐 is the on'yomi.