▪ I.† ˈdullen,ppl.a.Obs.rare. [irreg.] =prec. 1602Davison Rhapsody (1611) 70 And beating oft my dullen weary braine. ▪ II.dullen,v.rare.|ˈdʌlən| [f. dull a. + -en5.] trans. To make dull, to dull. 1832L. Hunt Sir R. Esher (1850) 464 His glossy locks were now dullened and mixed with grey.