Merriam-Webster Collegiate Dictionary - stoma

 noun  (plural ~ta; also ~s)  Etymology: New Latin, from Greek ~t-, ~ mouth  Date: circa 1684  1. any of various small simple bodily openings especially in a lower animal  2. one of the minute openings in the epidermis of a plant organ (as a leaf) through which gaseous interchange takes place; also the opening with its associated cellular structures  3. an artificial permanent opening especially in the abdominal wall made in surgical procedures