This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
墔 combines 土 (earth) with 崔, which likely contributes sound. The exact historical development is uncertain.
The left side is earth 土, and the right side 崔 contains a mountain 山 and a bird 隹. Picture a mound of earth piled up like a mountain where birds gather, but the exact meaning is unclear.
For サイ, imagine a sigh of uncertainty when looking at this rare kanji: sigh -> サイ, as you wonder what it means.
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