Isopod: a crustacean with seven pairs of legs. They use the legs to crawl.
Most isopods live in the water, though you can find some isopods living under logs, or in dark places.
The name Isopoda comes from the Greek ἴσος (iso), the same, and the Greek word for foot, ποδός (podos).
Still not sure what an isopod is? Neither am I. Perhaps this picture will help.