This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
禑 combines 示 (altar, spirit) with 禺, which may have contributed sound. The exact historical development is uncertain.
The left side 示 suggests a connection to spirits or altars, but the overall meaning is unclear. Imagine a mysterious altar with an unknown purpose.
For グ, imagine a good spirit at the altar: good -> グ, though the meaning remains uncertain.