This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
呩 combines 口 (mouth) with 示 (altar, show). The historical origin and original meaning are uncertain.
A mouth 口 beside an altar 示 might suggest speaking or showing something, but the exact meaning is unclear.
For シ, imagine a mouth 口 showing 示 a single sheet of paper: sheet -> シ, and the mouth is trying to communicate something.