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
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
Synonyms, antonyms and the broader and narrower relations for pyramid come from Princeton University’s WordNet. Full sources and licences.