[1] : The Collaborative International Dictionary of English v.0.48

darken \dark"en\ daumrk"'n, v. t. imp.  p. p. darkened
   -'nd; p. pr.  vb. n. darkening -ni^ng. as.
   deorcian. see dark, a.
   1. to make dark or black; to deprive of light; to obscure;
      as, a darkened room.
      1913 webster

            they locusts covered the face of the whole earth,
            so that the land was darkened.        --ex. x. 15.
      1913 webster

            so spake the sovran voice; and clouds began
            to darken all the hill.               --milton.
      1913 webster

   2. to render dim; to deprive of vision.
      1913 webster

            let their eyes be darkened, that they may not see.
                                                  --rom. xi. 10.
      1913 webster

   3. to cloud, obscure, or perplex; to render less clear or
      intelligible.
      1913 webster

            such was his wisdom that his confidence did seldom
            darkenhis foresight.                  --bacon.
      1913 webster

            who is this that darkeneth counsel by words without
            knowledge?                            --job.
                                                  xxxviii. 2.
      1913 webster

   4. to cast a gloom upon.
      1913 webster

            with these forced thoughts, i prithee, darken not
            the mirth of the feast.               --shak.
      1913 webster

   5. to make foul; to sully; to tarnish.
      1913 webster

            i must not think there are
            evils enough to darken all his goodness. --shak.
      1913 webster
see also:
darkened darkening dark 

[2] : The Collaborative International Dictionary of English v.0.48

darkening \dark"ening\, n.
   twilight; gloaming. prov. eng.  scot. --wright.
   1913 webster

[3] : WordNet (r) 2.0

darkening
     adj 1: becoming dark or darker as from waning light or clouding
            over; "the darkening sky"
     2: characterized by hopelessness; filled with gloom; "gloomy at
        the thought of what he had to face"; "gloomy predictions";
        "a gloomy silence"; "took a grim view of the economy";
        "the darkening mood" syn: gloomy, grim
     n : changing to a darker color syn: blackening
see also:
gloomy grim blackening 

[4] : Moby Thesaurus II by Grady Ward, 1.0

50 moby thesaurus words for "darkening":
   blackening, blocking the light, burial, burying, clouding,
   concealedness, concealment, covering, covering up, covertness,
   deception, denigration, dimming, eclipsing, extinguishment,
   hiddenness, hiding, interment, invisibility, masking, melanization,
   mystification, nigrification, obfuscation, obnubilation,
   obscuration, obscurement, obumbration, occultation, occulting,
   overcast, overclouding, overshading, overshadowing, overshadowment,
   putting away, screening, secrecy, secretion, shading, shadowing,
   smirch, smirching, smudge, smudging, smut, smutch, smutching,
   subterfuge, uncommunicativeness

Darkening >> D Words
Darkening, definition of term: Darkening
darkening_pag1.html