As proposed in forum #304645, the tag sulcus is currently being applied to posts featuring the coronal sulcus, the area of the penis right under the glans where the neck of the penis starts.
However, "sulcus" as a scientific term is usually used in reference to the furrows of the brain.
I wanted to propose a possible tag change from "sulcus" to "coronal sulcus" to avoid confusion. I would edit the wiki to more accurately reflect this change.
However, I also understand that tag overpopulation is a serious problem and that too many anatomical tags would bloat the site.
If "coronal sulcus" is too niche and scientific of a term, we could also consider the slightly-more-colloquial "neck of penis" as a potential candidate.
I wanted to make a forum post to gauge others' opinions on the matter before requesting an alias.