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Can someone tell me what the notation "ー・" means?

It's all over this article:
[大辞林「いう【言う・云う・謂う】」](https://kotobank.jp/word/%E8%A8%80%E3%81%86%E3%83%BB%E4%BA%91%E3%81%86%E3%83%BB%E8%AC%82%E3%81%86-201316#E5.A4.A7.E8.BE.9E.E6.9E.97.20.E7.AC.AC.E4.B8.89.E7.89.88)
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2017-11-15T00:33:48.960
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dictionary
What is the meaning of ー・
It simply means that it should be replaced by 言, 云 or 謂 in actual usage.

The notation is used exclusively in some dictionaries to avoid looking
repetitive in giving example phrases/sentences for the entry word.

(Of course, one could argue that the use of the same notation over and over
looks repetitive, too.)
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2017-11-15T00:40:26.000
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2017-11-15T00:40:26.000
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This dictionary definition, which you quoted, looks a bit half-baked.

* * *

Have a look at [大辞泉 for
話す](https://kotobank.jp/word/%E8%A9%B1%E3%81%99-603525#E3.83.87.E3.82.B8.E3.82.BF.E3.83.AB.E5.A4.A7.E8.BE.9E.E6.B3.89).

It first defines the root (constant) part:

> はな・す

And then uses it in examples:

> 「電話で―・す」
>
> 「父に―・してから返事する」

Where the part before the dot is constant and the ending is
conjugated/inflected.

* * *

Back to the example from the question, it should define い・う for the examples
to make sense.
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