mús
This might be just a supplemental entry adding to an entry in the Main Volume.
Related §§ in Wright's OE Grammar:
§3,
§5,
In the OE text, the length is:indicated by acute accentsindicated by macronsnot indicated.
mús
; I. AddSe micela ylp . . . ondrǽt him for þearle, gif hé gesihð áne mús, ðeáh ðe seó mús ne mage his micelnysse derian. Hml. A. 64, 258. Wiþ weartum, genim hundes micgean and múse blód, meng tósomne, smire mid, Lch. ii. 322, 12. Cwóman Indisce mýs ín þá fyrd in foxa gelícnisse mures Indici in castra pergebant uulpibus similes, Nar. 16, 5.
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A Combined List of Abbreviations.

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A Combined List of Abbreviations.