glottis n 1: the vocal apparatus of the larynx; the true vocal folds and the space between them where the voice tone is generated
Glottis \Glot"tis\, n. [NL., fr. Gr. ?, ?, from ?, ?, the tongue. See {Gloss} an explanatory remark.] (Anat.) The opening from the pharynx into the larynx or into the trachea. See {Larynx}. [1913 Webster]