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to pour into; to wash down (food)
to insert (e.g. into a data stream); to integrate
コンクリートを型に流し込んで固めた。
I poured concrete into the mold and let it set.
苦い薬を水で一気に流し込んだ。
I washed the bitter medicine down with water in one gulp.
熱い金属は慎重に扱い一気に流し込まない。
Handle hot metal carefully and don't pour it in all at once.