From The Collaborative International Dictionary of English v.0.48 :
ostracise \os"tra*cise\, v. t.
Same as ostracize. [Chiefly Brit.]
[PJC]
From WordNet (r) 3.0 (2006) :
ostracise
v 1: expel from a community or group [syn: banish, ban,
ostracize, ostracise, shun, cast out, blackball]
2: avoid speaking to or dealing with; "Ever since I spoke up, my
colleagues ostracize me" [syn: ostracize, ostracise]