Water is a transparent and nearly colorless chemical substance that is the main constituent of Earth's streams, lakes, and oceans, and the fluids of most living organisms. Its chemical formula is H2O, meaning that its molecule contains one oxygen and two hydrogen atoms, that are connected by covalent bonds.
1. recently born; called also neonatal. 2. newborn infant. postmature newborn (post-term newborn) post-term infant. premature newborn (preterm newborn) preterm infant.
Medical Definition of NICU. NICU: Newborn, or Neonatal, Intensive Care Unit, an intensive care unit designed for premature and ill newborn babies. Less often, NICU may refer to a Neurologic Intensive Care Unit. Last Editorial Review: 5/13/2016.