name of a mountain
岻 is a rare kanji used primarily as a mountain name. Its standalone meaning is tied to that specific place name rather than a general concept.
岻 combines 山 (mountain) with 氐, which likely contributes the sound. The character was probably created to write a specific mountain name.
The mountain radical 山 on the left and the phonetic 氐 on the right together point to a mountain name. Picture a sign on a mountain trail with 岻 written on it, marking the peak.
For ジ, imagine a mountain named after a person called Gee: Gee -> ジ, and the mountain 岻 is named after them.