hemopericardium
noun
he·mo·peri·car·di·um
variants:
or chiefly British haemopericardium \ -ˌper-ə-ˈkärd-ē-əm 
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plural hemopericardia\ -ē-ə
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Medical Definition of hemopericardium
: blood in the pericardial cavity
— called also hematopericardium