The Collaborative International Dictionary of English v.0.48:

Pyramid \Pyr"a*mid\, n. [L. pyramis, -idis, fr. Gr. ?, ?, of
   Egyptian origin: cf. F. pyramide.]
   [1913 Webster]
   1. A solid body standing on a triangular, square, or
      polygonal base, and terminating in a point at the top;
      especially, a structure or edifice of this shape.
      [1913 Webster]

   2. (Geom.) A solid figure contained by a plane rectilineal
      figure as base and several triangles which have a common
      vertex and whose bases are sides of the base.
      [1913 Webster]

   3. pl. (Billiards) The game of pool in which the balls are
      placed in the form of a triangle at spot. [Eng.]
      [1913 Webster]

   4. (Finance) a fraudulent investment scheme in which the
      manager promises high profits, but instead of investing
      the money in a genuine profit-making activity, uses the
      money from later investors to pay the profits to earlier
      investors; -- also called pyramid scheme or pyramid
      operation. This process inevitably collapses when
      insufficient new investors are available, leaving the
      later investors with total or near-total losses of their
      investments. The managers usually blame government
      regulations or interference for the collapse of the
      scheme, rather than admit fraud.
      [PJC]

   Altitude of a pyramid (Geom.), the perpendicular distance
      from the vertex to the plane of the base.

   Axis of a pyramid (Geom.), a straight line drawn from the
      vertex to the center of the base.

   Earth pyramid. (Geol.) See Earth pillars, under Earth.


   Right pyramid (Geom.) a pyramid whose axis is perpendicular
      to the base.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Pyramid \Pyr"a*mid\, v. i. (Speculation)
   To enlarge one's holding or interest in a series of
   operations on a continued rise or decline by using the
   profits to buy or sell additional amounts on a margin, as
   where one buys on a 10% margin 100 shares of stock quoted at
   100, holds it till it rises to 105, and then uses the paper
   profit to buy 50 shares more, etc. The series of operations
   constitutes a pyramid. A similar process of reinvesting gains
   or winnings (as of a gamble), but not involving operation on
   margin, is called a parlay.
   [Webster 1913 Suppl. +PJC]

The Collaborative International Dictionary of English v.0.48:

Pyramid \Pyr"a*mid\, v. t. (Speculation)
   To use, or to deal in, in a pyramiding transaction. See
   Pyramid, v. i.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

pyramid
    n 1: a polyhedron having a polygonal base and triangular sides
         with a common vertex
    2: (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
    3: a massive monument with a square base and four triangular
       sides; begun by Cheops around 2700 BC as royal tombs in
       ancient Egypt [syn: Pyramid, Great Pyramid, Pyramids of
       Egypt]
    v 1: enlarge one's holdings on an exchange on a continued rise
         by using paper profits as margin to buy additional amounts
    2: use or deal in (as of stock or commercial transaction) in a
       pyramid deal
    3: arrange or build up as if on the base of a pyramid
    4: increase rapidly and progressively step by step on a broad
       base

Moby Thesaurus II by Grady Ward, 1.0:

219 Moby Thesaurus words for "pyramid":
   add to, aggrandize, amplify, animal kingdom, antenna tower,
   anthill, arch, architecture, augment, bank, bank up, barbican,
   barrow, be caught short, be short, beehive tomb, belfry,
   bell tower, belong, bone house, boost, boundary stone, box grave,
   brass, broaden, bucket, bucketshop, build, build up, building,
   burial, burial chamber, burial mound, bust, cairn, campanile,
   catacombs, cenotaph, chain of being, charnel house, cist,
   cist grave, class structure, cock, colossus, column, construct,
   construction, cromlech, cross, crypt, cup, cupola, cyclolith,
   deep six, deposit margin, derrick, dokhma, dolmen, domain, dome,
   drift, dune, edifice, embankment, enlarge, erection, establishment,
   exalt, expand, extend, fabric, fatten, fill out, fire tower,
   footstone, go long, grave, gravestone, haycock, haymow, hayrick,
   haystack, headstone, heap, heap up, hierarchy, hike, hike up, hill,
   hoarstone, hold on, house, house of death, increase, inflate,
   inscription, jack up, jump up, kingdom, lantern, last home,
   lengthen, lighthouse, long home, low green tent, low house,
   make a killing, make a scoop, margin up, marker, martello,
   martello tower, mass, mast, mastaba, mausoleum, maximize, megalith,
   memento, memorial, memorial arch, memorial column, memorial statue,
   memorial stone, menhir, minaret, mineral kingdom, miss the market,
   molehill, monolith, monstrance, monument, mound, mountain, mow,
   mummy chamber, narrow house, natural hierarchy, necrology, obelisk,
   obituary, observation tower, operate, ossuarium, ossuary,
   overstay the market, packaged house, pagoda, parlay, passage grave,
   pecking order, pilaster, pile, pile up, pillar, pinnacle, pit,
   plaque, play the market, plunge, pole, power structure, prefab,
   prefabrication, prize, put up, pylon, raise, realm, reliquary,
   remembrance, resting place, ribbon, rick, rostral column, scalp,
   scoop the market, sepulcher, shaft, shaft grave, shrine,
   skyscraper, snowdrift, speculate, spire, stack, stack up, stag,
   stag the market, standpipe, steeple, stela, stone, structure,
   stupa, superstructure, tablet, take a flier, television mast,
   testimonial, thicken, tomb, tombstone, tope, tour, tower,
   tower of silence, trade on margin, trophy, tumulus, turret, up,
   vault, vegetable kingdom, venture, water tower, windmill tower,
   windrow