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to get dirty; to become dirty
to become sullied; to become corrupted; to lose one's chastity
「汚れる」 has another reading with different meanings.
服が泥で汚れてしまった。
My clothes got dirty with mud.
権力闘争で彼の心が汚れていく。
His heart is becoming corrupted through the power struggle.
手が汚れているから洗う。
My hands are dirty so I'll wash them.