1. The act of banishing or excluding someone: "In ancient Greece, the banishment was by popular vote of the people regarding a citizen who was considered dangerous to the state; usually, the vote was used to get rid of potential tyrants or political rivals."

"The banished person had to leave (or face death) but he was allowed to keep ownership of his property and he could return when his ostracism period was over."

2. Etymology: a method of 10-year banishment in ancient Athens, by which the Greek citizens got together and wrote the names of men they considered to be dangerous to the state on potsherds or tiles, and a man whose name turned up often enough was sent away. From Greek ostrakismos, from ostrakizein, "to ostracize", from ostrakon, "tile, potsherd" and related to osteon, "bone" and ostreion, "oyster" or "oyster shell".