/ˌepiˈkärdēəm/
Noun, pl. epicardia
1. Describes the outer layer of heart tissue. When considered as a part of the pericardium, it is the inner layer, or visceral pericardium, continuous with the serous layer. (wikipedia.org)
2. A serous membrane that forms the innermost layer of the pericardium and the outer surface of the heart. (Google Dictionary)
3. The innermost of the two layers of the pericardium. (wordnetweb.princeton.edu)
Word origin: From Greek; epi- outer, cardium heart.