0 a type of sea creature with a hard rounded shell shaped like a horseshoe or the letter U, five pairs of legs, and a long tail: --
Prehistoric trilobites looked similar to horseshoe crabs.
The horseshoe crab uses its ice-pick-like tail to steer in the water and to right itself should it be overturned in the sand.
Environmentalists say more must be done to protect horseshoe crabs because they provide vital food for migratory shorebirds.