This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 犓 is uncertain. It visually combines 牜 (cow) and 芻, but the original semantic and phonetic roles are unclear.
With no clear meaning, picture a cow (牜) chewing (芻 looks like grass being chewed) as a placeholder image.
For ス, imagine a cow named Sue chewing grass: Sue -> ス.
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