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busy (phone)
in talks; discussion underway
何度かけても話中で全然繋がらない。
No matter how many times I call, the line is busy.
彼の電話は三十分以上も話中だった。
His phone was busy for thirty minutes.
話中だったのでしばらく後でかけ直した。
The line was busy, so I called back later.