A worm hole worm is a worm that lives in a worm hole.
Worm hole worms' bodies are made out of spacetime and they can tunnel through spacetime to create worm holes. They then close off the worm holes and live in a pocket universe.
Worm hole worms feed on spacetime; spacetime is always producing particles and antiparticles that annihilate each other. However, when worm hole worms eat spacetime, it creates more particles and antiparticles then normal. So many are created that the energy produced when there annihilated is enough to destroy a planet. In some cases whole galaxies have been destroyed by hoards of worm hole worms.