Frustum

In geometry, a frustum (Latin for 'morsel'; pl. frusta or frustums), often incorrectly spelled as frustrum or frustrums, is the portion of a solid (normally a pyramid or a cone) that lies between two parallel planes cutting the solid. In the case of a pyramid, the base faces are polygonal and the side faces are trapezoidal. A right frustum is a right pyramid or a right cone truncated perpendicularly to its axis; otherwise, it is an oblique frustum.

In a truncated cone or truncated pyramid, the truncation plane is not necessarily parallel to the cone's base, as in a frustum.

If all its edges are the same length, then a frustum becomes a prism (possibly oblique or/and with irregular bases).