mægen-fæst
This might be just a supplemental entry adding to an entry in the Main Volume.
Related §§ in Wright's OE Grammar:
In the OE text, the length is:indicated by acute accentsindicated by macronsnot indicated.
mægen-fæst
AddÞes eard nis eác ealles swá mægenfæst hér on úteweardan þǽre eorðan brádnesse swá swá heó is tómiddes on mægen-fæstum eardum, þǽr man mæg fæstan freólícor þonne hér, Hml. S. 13, 106-109.
This is a supplementary entry with editorial changes to an entry in the main volume of the dictionary. Look under the 'Possibly connected entries' below, or for the same headword in the list to the left.

A Combined List of Abbreviations.

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A Combined List of Abbreviations.