椎
ツイ, スイ, つち, う.つ, しい

oak, mallet

JLPT1 G7 S12 F1911

As per 隹# (exert downward pressure) + 木 tree/wood → *strike* down with a wooden *mallet* → *hammer*. *Vertebra* is a borrowed meaning, as is the variety of oak known as *pasania* or *chinquapin*.

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