on-bútan
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.
on-bútan
I. add: 1. prep. a. with dat. Þá munecas lágon onbúton þám weófode, Chr. 1083; P. 215, 13. b. with acc. Hí wendon onbúton Tenet, Chr. 1046; P. 166, 12. 2. as adv. Hí him férdon onbúton swá swá hí sylf woldon, Chr. 1001; P. 133, 27. Eówer wiðerwinna færð him onbútan adversarius vester circuit, Hml. A. 52, 54. II. AddÞysse wyrte wyrttruman man sceal niman onbútan midne sumur, Lch. i. 260, 3. III. add: with another adverb Ǽghwǽr onbútan circumquaque, An. Ox. 2, 251. III a. v. þǽr-onbútan; á-bútan.
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A Combined List of Abbreviations.