pyramid

1. (geometry) A solid with triangular lateral faces and a polygonal (often square or rectangular) base.countableuncountable

2. (by extension) Any structure or diagram with many members at the bottom and progressively fewer towards the top.Examples: "The company was organized as a pyramid, with a CEO in charge of four directors, each heading up a department."; "They sit looking at the empty plate that had held a pyramid of sesame cakes. They have eaten them all."; "A telephone pyramid is now being formed to fill this need. Once a representative group of community people decide a crisis exists […] a list of people will be called, who in turn will call a small number of others from a list already in their possession. This process continues untill as much of the community as possible has been notified. The numbers will be kept in strict confidence, with no one other than the organizers having the entire list. Individual callers will only have a few names and numbers."broadlycountableuncountable

3. (neuroanatomy) A medullary pyramid, the medial-most bumps on the ventral side of the medulla oblongatacountableuncountable

4. (UK, dated) The game of pool in which the balls are placed in the form of a triangle at spot.UKcountabledateduncountable

5. (card games, uncountable) Alternative letter-case form of Pyramid. (a solitaire card game)alt-ofuncountable

6. (card games) The triangular layout of cards in the game of Pyramid.Examples: "Build your pyramid with all cards face down, except the cards in the bottom row."countableuncountable