険
ケン, けわ.しい

precipitous, inaccessible place, impregnable position, steep place, sharp eyes

JLPT3 G5 S11 F707

As per 僉# (assemble) + 阜 piled earth → assemblage/convergence of cliff walls in a narrow mountain pass → *narrow pass* → *strategic point*; *rugged*; *dangerous*; *obstruction*.

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