bad blood

Synonym discussion

Sense: noun/1

While all five words describe negative feelings between people, they differ in tone and scope. Bad blood is the most conversational — it points specifically to a feud or tension that has lasted because of something that happened in the past. Animosity is more formal and broader: two political rivals may feel animosity without any single past incident to blame. Hostility is the strongest of the group, often implying active aggression, not just cold silence. Resentment focuses on the injured party's sense of injustice — you resent someone because you believe they wronged you. A grudge is typically one-sided: one person nurses a grudge against another, who may not even know about it. In a workplace, long-standing bad blood between two managers might show as frosty meetings and avoided eye contact; a grudge, by contrast, could be one colleague silently fuming over a promotion denied ten years ago.

Etymology

The phrase comes from the old medical belief that a person's physical and mental health depended on the quality of their blood. 'Bad blood' was thought to cause disease. By the early 1600s, the expression had shifted to a purely figurative meaning — ill feeling or hostility between people — and the medical sense faded away.