noun (n)

• a minute epidermal pore in a leaf or stem through which gases and water vapor can pass(noun.plant)

  Synonym:
  pore, stomate
  

  source: wordnet30
• a mouth or mouthlike opening (especially one created by surgery on the surface of the body to create an opening to an internal organ)(noun.body)

  source: wordnet30
• One of the minute apertures between the cells in many serous membranes.(noun)

  source: webster1913