ETYM Latin pyramis, -idis, from Greek pyramis, of Egyptian origin: cf. French pyramide.
1. A massive memorial with a square base and four triangular sides; built as royal tombs in ancient Egypt.
2. A polyhedron having a polygonal base and triangular sides with a common vertex.

In geometry, a three-dimensional figure with triangular side-faces meeting at a common vertex (point) and with a polygon as its base. The volume V of a pyramid is given by V = 1/3Bh, where B is the area of the base and h is the perpendicular height. Pyramids are generally classified by their bases. For example, the Egyptian pyramids have square bases, and are therefore called square pyramids. Triangular pyramids are also known as tetrahedra (“four sides”).

Four-sided building with triangular sides. Pyramids were used in ancient Egypt to enclose a royal tomb; for example, the Great Pyramid of Khufu/Cheops at El Gîza, near Cairo, 230 m/755 ft square and 147 m/481 ft high. The three pyramids at Gîza were considered one of the Seven Wonders of the World. In Babylon and Assyria, broadly stepped pyramids (ziggurats) were used as the base for a shrine to a god: the Tower of Babel was probably one of these.
Truncated pyramidal temple mounds were also built by the ancient Mexican and Peruvian civilizations, for example, at Teotihuacan and Cholula, near Mexico City, which is the world's largest in ground area (300 m/990 ft base, 60 m/195 ft high). Some New World pyramids were also used as royal tombs, for example, at the Mayan ceremonial center of Palenque.

1. To arrange or build up as if on the base of a pyramid.
2. To enlarge one's holdings on an exchange on a continued rise by using paper profits as margin to buy additional amounts.
3. To increase rapidly and progressively step by step on a broad base.
4. To use or deal in (as of stock or commercial transaction) in a pyramid deal.