The Collaborative International Dictionary of English v.0.48:
Melaena \Me*lae"na\, n. [NL., fr. Gr. me`las, m., me`laina, f., black.] (Med.) A discharge from the bowels of black matter, consisting of altered blood. [1913 Webster]WordNet (r) 3.0 (2006):
melaena n 1: abnormally dark tarry feces containing blood (usually from gastrointestinal bleeding) [syn: melena, melaena]