I've seen it called a double cone. I've also seen cones with their points together called a double cone.

Possibly more helpful than my earlier facetious remark - name for two cones joined at base - Google Search

bicone Equivalently, a bicone is the surface created by joining two congruent, right, circular cones at their bases. A bicone has circular symmetry and orthogonal bilateral symmetry. And that concludes the lessons for the day ...