1. Any of several small insectivorous mammals of the subfamily Erinaceinae, native to Eurasia and Africa and naturalized in New Zealand, having dense erectile spines covering the back and sides and characteristically rolling into a ball for protection.

2. Any of several spiny animals, such as the porcupine, that are similar to the hedgehog.

3. A well fortified military position.

4. An antisubmarine weapon consisting of several rows of mortar-like dischargers positioned to fire in a circular pattern ahead of a ship.

5. An obstacle used against tanks and landing craft, consisting of three crossed iron bars welded or bolted together.