epicardium

noun, plural ep·i·car·di·a [ep-i-kahr-dee-uh] /ˌɛp ɪˈkɑr di ə/. Anatomy.

1. the inner serous layer of the pericardium, lying directly upon the heart.

noun plural -dia (-dɪə)

1. anatomy the innermost layer of the pericardium, in direct contact with the heart

n. pl. ep•i•car•di•a (-dē-ə)

1. The inner layer of the pericardium that is in contact with the surface of the heart.visceral layer