Source : Webster's Revised Unabridged Dictionary (1913)

Frustum \Frus"tum\, n.; pl. L. {Frusta}, E. {Frustums}. [L.
   fruslum piece, bit.]
   1. (Geom.) The part of a solid next the base, formed by
      cutting off the, top; or the part of any solid, as of a
      cone, pyramid, etc., between two planes, which may be
      either parallel or inclined to each other.

   2. (Arch.) One of the drums of the shaft of a column.

Source : WordNet®

frustum
     n : a truncated cone or pyramid; the part that is left when a
         cone or pyramid is cut by a plane parallel to the base
         and the apical part is removed
     [also: {frusta} (pl)]

frusta
     See {frustum}