Mawson, C.O.S., ed. (1870–1938). Roget’s International Thesaurus. 1922.

Class VI. Words Relating to the Sentient and Moral Powers
Section II. Personal Affections
1. Passive Affections

843. Dullness.

   NOUN:DULLNESS or dulness, heaviness, flatness; infestivity [See Dejection], stupidity [See Imbecility. Folly]; want of originality; dearth of ideas.
  prose, matter of fact; heavy book, conte à dormir debout [F.]; commonplace, platitude.
   VERB:BE DULL &c. adj.; hang fire, fall flat; platitudinize, prose, take au sérieux [F.], be caught napping.
  RENDER DULL &c. adj.; damp, depress, throw cold water on, lay a wet blanket on; fall flat upon the ear.
   ADJECTIVE:DULL, – as ditch water; jejune, dry, unentertaining, uninteresting, un- lively, heavy-footed, elephantine; slow of comprehension; insipid, tasteless, slow as cold molasses [colloq.], logy [U. S.]; unimaginative; insulse; dry as dust; prosy, prosing, prosaic; matter-of-fact, commonplace, platitudinous, pointless; “weary, stale, flat, and unprofitable” [Hamlet].
  STUPID, slow, flat, humdrum, monotonous; melancholic [See Dejection]; stolid [See Imbecility. Folly]; plodding.
  1. Davus sum non Ædipus.
  2. Fain would I write but that I fear to pall.—Cynic’s Calendar