sours
v.
（使某物）变酸，变馊， （使某人）阴郁( sour的第三人称单数 );
关系、态度、人等（使）变坏，恶化;
例句:
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It further sours the sourest White House-Capitol Hill relationship of modern political history.
来自WSJ
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If anything sours the relationship, it is likely to be real differences in their world-views.
如果有什么东西能够破坏这种关系的话，那可能就是他们世界观方面存在的实质性差异。
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A: Two whiskey sours, a Scotch on the rocks, and a martini.
甲: 两杯威士忌加柠檬汁 、 一杯苏格兰威士忌加冰块 、 一杯马提尼鸡尾酒.
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Two whiskey sours, a Scotch on the rocks, and a martini.
两杯威士忌加柠檬汁 、 一杯苏格兰威士忌加冰块 、 一杯马提尼鸡尾酒.
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In every hierarchy the cream rises until it sours.
来自BBC
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Potential buyers don't return calls, business sours or you face repeated rejection.
来自WSJ