Source : Webster's Revised Unabridged Dictionary (1913)

Epicardium \Ep`i*car"di*um\, n. [NL., fr. Gr. 'epi` upon + ?
   heart.] (Anat.)
   That of the pericardium which forms the outer surface of the
   heart; the cardiac pericardium.

Source : WordNet®

epicardium
     n : the innermost of the two layers of the pericardium [syn: {visceral
         pericardium}]
     [also: {epicardia} (pl)]