English edit

Etymology edit

From dull +‎ -en.

Pronunciation edit

Verb edit

dullen (third-person singular simple present dullens, present participle dullening, simple past and past participle dullened)

  1. (transitive, nonstandard) To make dull or duller; to dull.
  2. (intransitive, nonstandard) To become dull or duller; to dull.

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