stoma
     n 1: a minute epidermal pore in a leaf or stem through which
          gases and water vapor can pass [syn: {stomate}, {pore}]
     2: a mouth or mouthlike opening (especially one created by
        surgery on the surface of the body to create an opening to
        an internal organ)
     [also: {stomata} (pl)]
Source: WordNet® 2.0