foramen definition
Medical Definition of FORAMEN. : a small opening, perforation, or orifice: fenestra 1.â foÂ·ramÂ·iÂ·nal \fÉ-Ëram-Én-Él\ adjective.edical Definition of FORAMEN. : a small opening, perforation, or orifice: fenestra 1. â foÂ·ramÂ·iÂ·nal \fÉ-Ëram-Én-Él\ adjective.