1. a small opening or mouth-like aperture in a body part or organ
Usage: medical; anatomical

Examples

• The ostium of the fallopian tube opens into the peritoneal cavity.
• Each ostium in the heart allows blood to flow between chambers.
• The surgeon examined the ostium for any signs of blockage.
• Multiple ostia were visible on the radiographic image.
• The ostium appeared dilated during the medical examination.