Definitions for "Trilobite"
Any one of numerous species of extinct arthropods belonging to the order Trilobita. Trilobites were very common in the Silurian and Devonian periods, but became extinct at the close of the Paleozoic. So named from the three lobes usually seen on each segment.
A major group of fossil arthropods that lived during the Cambrian to Permian times. Rather like a cross between a wood-louse and a lobster - they were major predators in the Cambrian shallow seas.
an extinct group of marine arthropods that lived from 590 to 280 million years ago. Trilobites were small (usually) benthic scavengers.