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to pile up; to make a heap; to lay (e.g. bricks)
to acquire (e.g. experience); to build (a reputation)
倉庫に箱を積み上げた。
I piled up boxes in the warehouse.
地道に経験を積み上げる。
To steadily accumulate experience.
学生は努力を積み上げている。
The student is building up effort.