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to grow thickly; to be overgrown; to thrive; to grow in abundance
廃屋の庭に雑草が生い茂った。
Weeds grew thickly in the garden of the abandoned house.
川沿いの草が生い茂っている夏の光景だ。
It is a summer scene of grass growing densely along the river.
放置された公園では雑木が生い茂るのが問題になっている。
In the neglected park, overgrown shrubs have become a problem.