This is a disambiguation page for the biological term. For the 2018 horror movie, see Antrum (film) In biology, antrum is a general term for a cavity or chamber, which may have specific meaning in reference to certain organs or sites in the body. In vertebrates, it may refer specifically to: Antrum follicularum, the cavity in the epithelium that envelops the oocyte Mastoid antrum, a cavity between the middle ear and temporal bone in the skull Stomach antrum, either Pyloric antrum, the lower portion of the stomach...