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to push into; to cram into; to stuff into; to crowd into
to break in; to burgle; to burglarize
スーツケースに服を押しこんでやっと閉めた。
I crammed clothes into the suitcase and finally managed to close it.
満員電車に無理やり体を押しこんで乗り込んだ。
I forced my way into the packed train.
本棚にもう一冊を押しこむ隙間がなかった。
There was no space left to squeeze another book onto the shelf.