When a double cone is sliced at the apex by a plane perpendicular to the base of the cone, the resulting conic section is hyperbola
What is hyperbola?
A double cone can be made to "pinch" its two halves together at their top point by slicing it through the apex with a plane perpendicular to the base. In this instance, the pinching results in a degenerate conic, which produces a hyperbola with infinitely near branches.
Imagine the hyperbola's two branches coming out of the apex point and expanding eternally to either side yet never getting too far apart. The essence of the "collapsed" cone shape at the apex is captured by this degenerate hyperbola.
Consequently, even though it may not make sense, the degenerate conic that forms in this situation is indeed a hyperbola—albeit one with infinitely near branches.