What is "stunjelly"

In the Dungeons & Dragons fantasy role-playing game, the Stunjelly is an ooze. They are relatives of the Gelatinous cube that were created by a forgotten mage to act as sentries. Stunjellies resemble thick, grey, slightly transparent stone walls. Similar to the Gelatinous Cube, they do not have quite as amorphous forms as other oozes, and must retain their geometric, wall-esque shape. They live underground, and typically lurk in hallways, devouring all in their path.