Medical Definition of Foramen. auditory foramen, external the external acoustic meatus. foramen [fo-ra´men] (pl.
fora´mina) (L.) a natural opening or passage, especially one into or through a bone. In human anatomy, the omental foramen (epiploic foramen, foramen of Winslow after the anatomist Jacob B. Winslow, or uncommonly aditus; Latin: Foramen epiploicum), is the passage of communication, or foramen, between the greater sac (general cavity (of the abdomen)), and the lesser sac Borders. The plural of foramen is foramina. apical foramen an opening at or near the apex of the root of a tooth. Medical Author: William C. Shiel Jr., MD, FACP, FACR; Foramen: A natural opening. aortic foramen aortic hiatus. Medical definition of foramen spinosum: an aperture in the greater wing of the sphenoid that gives passage to the middle meningeal artery. Although a foramen is usually through bone, it can be an opening through other types of tissue, as with the foramen ovale in the heart.