This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
齘 combines 齒 (teeth) with 介, which likely contributes a phonetic element. The exact historical development is uncertain.
The left side 齒 suggests teeth, and the right side 介 looks like a person between boundaries. Imagine teeth grinding or clenching, as if caught between something, though the actual meaning is uncertain.
For カイ, picture a person with teeth clenched, letting out a sharp 'kai!' sound: kai -> カイ.
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