Aditus ad infundibulum is a medical term that refers to a narrow passage connecting two anatomical structures. While there aren't many direct synonyms for this specific terminology, we can explore alternative phrases that capture a similar concept. For instance, a related term is "conduit", which can depict a tube or channel that allows the passage of substances. Another substitute could be "connecting passage", emphasizing the link between different areas. Additionally, "narrow junction" or "interconnecting tunnel" can convey a comparable meaning. Although there might not be exact synonyms, these phrases effectively communicate the concept of a restricted passageway connecting two points.