pyramid has 2 distinct synonyms spread across 1 of its 7 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
enlarge one's holdings on an exchange on a continued rise by using paper profits as margin to buy additional amounts
use or deal in (as of stock or commercial transaction) in a pyramid deal
arrange or build up as if on the base of a pyramid
Synonyms, antonyms and the broader and narrower relations for pyramid come from Princeton University’s WordNet. Full sources and licences.
increase rapidly and progressively step by step on a broad base
a polyhedron having a polygonal base and triangular sides with a common vertex
(stock market) a series of transactions in which the speculator increases his holdings by using the rising market value of those holdings as margin for further purchases
a massive monument with a square base and four triangular sides; begun by Cheops around 2700 BC as royal tombs in ancient Egypt