What does ostracize mean?

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From our dictionary:

os•tra•cize

Pronunciation: (os'tru-sIz"), [key]
v.t., -cized, -ciz•ing.
1. to exclude, by general consent, from society, friendship, conversation, privileges, etc.: His friends ostracized him after his father's arrest.
2. to banish (a person) from his or her native country; expatriate.
3. (in ancient Greece) to banish (a citizen) temporarily by popular vote. Also, esp. Brit.,os'tra•cise".