irþ
This might be just a supplemental entry adding to an entry in the Main Volume.
In the OE text, the length is:indicated by acute accentsindicated by macronsnot indicated.
irþ
Add:I. ploughing On manegum landum tilð bið redre ðonne on óðrum; ge yrðe tíma hrædra, Angl. ix. 259, 10. Yrðe georne forðian, 261, 21. Yrde, 5. II. a crop ; seges Eard, Bd. 4, 28; Sch. 521, 15. [v N.E.D. earth.] v. bén-irþ, for-irþ.
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A Combined List of Abbreviations.

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A Combined List of Abbreviations.