Opening in the roof of a cave, cavern or other underground void through which air is sucked in and expelled in a rhythmic manner similar to inhalation and exhalation of breath [20]. Related to blow hole and steam hole. Synonyms: (French.) trou souffleur; (German.) Luftloch, (Greek.) anapneousa opi spileou; (Spanish.) respirador; (Turkish.) esintili delik.