ge-stun
This might be just a supplemental entry substituting part of an entry in the Main Volume.
In the OE text, the length is:indicated by acute accentsindicated by macronsnot indicated.
ge-stun
Substitute: I. a deafening noise, crash Þæt swínlice gestun porcinus (paganorum) strepitus, Wrt. Voc. ii. 85, 31. Gestunum fragoribus (fratoribus, MS.), 150, 41. II. a storm, tempest, hurricane Þæt gestun and se storm and seó stronge lyft brecað bráde gesceaft hurricane and storm and tempest break up the wide world, Cri. 991. Dol swylteð, gif him Meotud þurh regn ufan of gestune lǽteð strǽle fleógan, Rä. 4, 56. Þurh gestun per turbinem, Wrt. Voc. ii. 68, 73. See next word.
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A Combined List of Abbreviations.

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A Combined List of Abbreviations.