The Collaborative International Dictionary of English v.0.48:

Truncated \Trun"ca*ted\, a.
   1. Cut off; cut short; maimed.
      [1913 Webster]

   2. (Min.) Replaced, or cut off, by a plane, especially when
      equally inclined to the adjoining faces; as, a truncated
      edge.
      [1913 Webster]

   3. (Zool.) Lacking the apex; -- said of certain spiral shells
      in which the apex naturally drops off.
      [1913 Webster]

   Truncated cone or Truncated pyramid (Geom.), a cone or
      pyramid whose vertex is cut off by a plane, the plane
      being usually parallel to the base.
      [1913 Webster]

WordNet (r) 3.0 (2006):

truncated pyramid
    n 1: a frustum formed from a pyramid