The Collaborative International Dictionary of English v.0.48:
Meconium \Me*co"ni*um\, n. [L., fr. Gr. ?, fr. ? poppy.] (Med.) (a) Opium. [Obs.] (b) The contents of the fetal intestine; hence, first excrement. [1913 Webster]WordNet (r) 3.0 (2006):
meconium n 1: thick dark green mucoid material that is the first feces of a newborn child