The Collaborative International Dictionary of English v.0.48:

Night \Night\ (n[imac]t), n. [OE. night, niht, AS. neaht, niht;
   akin to D. nacht, OS. & OHG. naht, G. nacht, Icel. n[=o]tt,
   Sw. natt, Dan. nat, Goth. nahts, Lith. naktis, Russ. noche,
   W. nos, Ir. nochd, L. nox, noctis, Gr. ny`x, nykto`s, Skr.
   nakta, nakti. [root]265. Cf. Equinox, Nocturnal.]
   1. That part of the natural day when the sun is beneath the
      horizon, or the time from sunset to sunrise; esp., the
      time between dusk and dawn, when there is no light of the
      sun, but only moonlight, starlight, or artificial light.
      [1913 Webster]

            And God called the light Day, and the darkness he
            called Night.                         --Gen. i. 5.
      [1913 Webster]

   2. Hence:
      (a) Darkness; obscurity; concealment.
          [1913 Webster]

                Nature and nature's laws lay hid in night.
                                                  --Pope.
          [1913 Webster]
      (b) Intellectual and moral darkness; ignorance.
      (c) A state of affliction; adversity; as, a dreary night
          of sorrow.
      (d) The period after the close of life; death.
          [1913 Webster]

                She closed her eyes in everlasting night.
                                                  --Dryden.
          [1913 Webster]

                Do not go gentle into that good night
                Rage, rage against the dying of the light.
                                                  --Dylan
                                                  Thomas.
          [PJC]
      (e) A lifeless or unenlivened period, as when nature seems
          to sleep. "Sad winter's night". --Spenser.
          [1913 Webster]

   Note: Night is sometimes used, esp. with participles, in the
         formation of self-explaining compounds; as,
         night-blooming, night-born, night-warbling, etc.
         [1913 Webster]

   Night by night, Night after night, nightly; many nights.
      [1913 Webster]

            So help me God, as I have watched the night,
            Ay, night by night, in studying good for England.
                                                  --Shak.
      [1913 Webster]

   Night bird. (Zool.)
      (a) The moor hen (Gallinula chloropus).
      (b) The Manx shearwater (Puffinus Anglorum).

   Night blindness. (Med.) See Hemeralopia.

   Night cart, a cart used to remove the contents of privies
      by night.

   Night churr, (Zool.), the nightjar.

   Night crow, a bird that cries in the night.

   Night dog, a dog that hunts in the night, -- used by
      poachers.

   Night fire.
      (a) Fire burning in the night.
      (b) Ignis fatuus; Will-o'-the-wisp; Jask-with-a-lantern.


   Night flyer (Zool.), any creature that flies in the night,
      as some birds and insects.

   night glass, a spyglass constructed to concentrate a large
      amount of light, so as see objects distinctly at night.
      --Totten.

   Night green, iodine green.

   Night hag, a witch supposed to wander in the night.

   Night hawk (Zool.), an American bird (Chordeiles
      Virginianus), allied to the goatsucker. It hunts the
      insects on which it feeds toward evening, on the wing, and
      often, diving down perpendicularly, produces a loud
      whirring sound, like that of a spinning wheel. Also
      sometimes applied to the European goatsuckers. It is
      called also bull bat.

   Night heron (Zool.), any one of several species of herons
      of the genus Nycticorax, found in various parts of the
      world. The best known species is Nycticorax griseus, or
      Nycticorax nycticorax, of Europe, and the American
      variety (var. naevius). The yellow-crowned night heron
      (Nyctanassa violacea syn. Nycticorax violaceus)
      inhabits the Southern States. Called also qua-bird, and
      squawk.

   Night house, a public house, or inn, which is open at
      night.

   Night key, a key for unfastening a night latch.

   Night latch, a kind of latch for a door, which is operated
      from the outside by a key.

   Night monkey (Zool.), an owl monkey.

   night moth (Zool.), any one of the noctuids.

   Night parrot (Zool.), the kakapo.

   Night piece, a painting representing some night scene, as a
      moonlight effect, or the like.

   Night rail, a loose robe, or garment, worn either as a
      nightgown, or over the dress at night, or in sickness.
      [Obs.]

   Night raven (Zool.), a bird of ill omen that cries in the
      night; esp., the bittern.

   Night rule.
      (a) A tumult, or frolic, in the night; -- as if a
          corruption, of night revel. [Obs.]
      (b) Such conduct as generally rules, or prevails, at
          night.

                What night rule now about this haunted grove?
                                                  --Shak.

   Night sight. (Med.) See Nyctolopia.

   Night snap, a night thief. [Cant] --Beau. & Fl.

   Night soil, human excrement; -- so called because in cities
      it is collected by night and carried away for manure.

   Night spell, a charm against accidents at night.

   Night swallow (Zool.), the nightjar.

   Night walk, a walk in the evening or night.

   Night walker.
      (a) One who walks in his sleep; a somnambulist; a
          noctambulist.
      (b) One who roves about in the night for evil purposes;
          specifically, a prostitute who walks the streets.

   Night walking.
      (a) Walking in one's sleep; sleep walking; somnambulism;
          noctambulism.
      (b) Walking the streets at night with evil designs.

   Night warbler (Zool.), the sedge warbler (Acrocephalus
      phragmitis); -- called also night singer. [Prov. Eng.]


   Night watch.
      (a) A period in the night, as distinguished by the change
          of watch.
      (b) A watch, or guard, to aford protection in the night.


   Night watcher, one who watches in the night; especially,
      one who watches with evil designs.

   Night witch. Same as Night hag, above.
      [1913 Webster]

WordNet (r) 3.0 (2006):

night watch
    n 1: a watch during the night (as from midnight to 8 a.m.) [syn:
         graveyard watch, middle watch, midwatch, night
         watch]