meconium (mi-koh-niŭm) n. the first stools of a newborn baby, which are sticky and dark green and composed of cellular debris, mucus, and bile pigments. m. aspiration a condition in which a baby inhales meconium into the lungs during delivery, which can cause plugs in the airway; the baby may become hypoxic. m. ileus obstruction of the ileum caused by thickened meconium in babies with cystic fibrosis.

meconium The first faecal material passed by a newborn mammal, which is usually dark green in colour.