Noun
the large opening at the base of the cranium through which the spinal cord passes
Source: WordNetNext, he takes a distressingly small Caucasian skull, shakes hard, and pushes mightily at the foramen magnum with his thumb. Source: Internet
The leakage can cause a lack of CSF pressure and volume which can allow the brain to descend through the foramen magnum in the occipital bone where the lower portion of the brain may impact on cranial nerve complexes causing a variety of sensory symptoms. Source: Internet
The foramen magnum migrated under the skull and more anterior. Source: Internet