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to run (of liquid); to spread; to bleed; to blot
to blur; to blot; to be blurred
to ooze; to well up (of tears, etc.)
to show through (of feelings, emotions, etc.); to reveal itself
万年筆のインクが湿った紙の上でにじんで読めなくなった。
The fountain pen ink bled on the damp paper and became unreadable.
感動の涙が目ににじんで舞台が霞んで見えてしまった。
Tears of emotion blurred my eyes and the stage looked hazy.
彼の表情には長年の苦労がにじみ出て隠しきれなかった。
Years of hardship showed through in his expression and couldn't be hidden.