undull

From Middle English undull, equivalent to un- (“not”) +‎ dull.

undull (comparative more undull, superlative most undull)

1. Not dull; sharp.

From un- +‎ dull.

undull (third-person singular simple present undulls, present participle undulling, simple past and past participle undulled)

1. (transitive) To make less dull (various senses).
   • 1654, Richard Whitlock, Zootomia; Or, Observations on the Present Manners of the English:

     It is a most musicall Modulator of all Intelligibles by her inventive Variations, undulling their Grossenesse, and subliming it into more refined Acceptablenesse to our own, or others understandings.

• “undull”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC.