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solid; robust; well-built
tight; taut
shrewd; calculating; astute
二人はがっちり手を握り合って誓った。
The two firmly clasped hands and made a vow.
がっちり稼いで将来に備えたいと思う。
I want to earn well and prepare for the future.
門はがっちり閉まっていて入れなかった。
The gate was firmly closed and I couldn't enter.