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（因行为令人震惊或反感）大家唯恐避之不及的人，被排斥的人
If you refer to someone as a leper, you mean that people in their community avoid them because they have done something that has shocked or offended people.
例句
The newspaper article had branded her a social leper not fit to be seen in company.
报纸上的这篇文章给她冠以“社交毒药”之名，称人皆不宜与其为伍。