1. Any of several small insectivorous mammals of the family Erinaceidae of Europe, Africa, and Asia, having the back covered with dense erectile spines 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.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.