noun / verb
pyramid
PEER-uh-mid/ˈpɪrəmɪd/
A structure that narrows from a broad base to a point.
The pyramid has a square base and triangular faces meeting at a point.

Etymology
Greek pyramis named the Egyptian monuments. The geometrical sense carries over their broad-based, tapering form to a solid whose triangular faces meet at a single point.
In context
That wide base and narrowing peak [music] of a pyramid is not just an iconic shape.
More examples
- The grocer stacks oranges in a pyramid.
- The club runs a pyramid scheme that pays members with new recruits' money.
- He pyramids his investments by borrowing against each new purchase.
Forms
pyramid · pyramids · pyramided · pyramiding
pyramidal adjective — Having the shape of a pyramid.