Transpiration

n.
  1. (Physiol.) The act or process of transpiring or excreting in the form of vapor; exhalation, as through the skin or other membranes of the body; as, pulmonary transpiration, or the excretion of aqueous vapor from the lungs. Perspiration is a form of transpiration.
  2. (bot.) The evaporation of water, or exhalation of aqueous vapor, from cells and masses of tissue.
  3. (Physics) The passing of gases through fine tubes, porous substances, or the like; as, transpiration through membranes.