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to be crowded; to be packed; to be congested; to be thronged (with)
to be complex; to be intricate
to go into; to go in; to put into
to become (completely)
to do thoroughly; to do sufficiently
to remain (silent, seated, etc.); to stay ...
朝の電車はいつも込んでいる。
The morning train is always crowded.
道が込んでいて遅くなりました。
The road was congested, so I was late.
年末はどこも込むから早めに予約した方がいい。
Everywhere gets crowded at year-end, so it's better to book early.