This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development is uncertain. The modern form combines ⻖ (mound/hill) with 夋, but the original meaning and component function are unclear.
With no clear meaning, picture a steep hill (⻖) with a strange shape (夋) that defies easy description—like a mysterious landmark.
For シュン, imagine a shun (シュン) sound echoing off the hill: the hill (⻖) shuns (シュン) any clear meaning.