a baby's first poop
, which tends to be brownish, greenish, or black. It's tarry, smells nasty, and stains like crazy.
Provided the baby gets lots of colostrum, it should clear within a few days or so, which is good, since if it lingers too long in that little bitty intestine, it can contribute to jaundice in the infant.
Occasionally, babies let loose a little bit before they are born, which can be very bad. Birth attendants look at the color of the amniotic fluid to determine if some meconium has been passed before the baby is born. If it is any color other than clear, great caution is in order, and the baby's throat may need to be suctioned to clear out the meconium once it is born. Rarely, babies die from meconium aspiration, which is a truly tragic thing.