The Collaborative International Dictionary of English v.0.48:

Sundog \Sun"dog`\, n. (Meteorol.)
   1. A luminous spot occasionally seen a few degrees from the
      sun, supposed to be formed by the intersection of two or
      more halos, or in a manner similar to that of halos.
      [1913 Webster]

   2. A fragmentary rainbow; a small rainbow near the horizon;
      -- called also dog and weathergaw.
      [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Dog \Dog\ (d[add]g or d[o^]g), n. [AS. docga; akin to D. dog
   mastiff, Dan. dogge, Sw. dogg.]
   1. (Zool.) A quadruped of the genus Canis, esp. the
      domestic dog (Canis familiaris).

   Note: The dog is distinguished above all others of the
         inferior animals for intelligence, docility, and
         attachment to man. There are numerous carefully bred
         varieties, as the akita, beagle, bloodhound,
         bulldog, coachdog, collie, Danish dog,
         foxhound, greyhound, mastiff, pointer,
         poodle, St. Bernard, setter, spaniel, spitz,
         terrier, German shepherd, pit bull, Chihuahua,
         etc. There are also many mixed breeds, and partially
         domesticated varieties, as well as wild dogs, like the
         dingo and dhole. (See these names in the Vocabulary.)
         [1913 Webster +PJC]

   2. A mean, worthless fellow; a wretch.
      [1913 Webster]

            What is thy servant, which is but a dog, that he
            should do this great thing?           -- 2 Kings
                                                  viii. 13 (Rev.
                                                  Ver. )
      [1913 Webster]

   3. A fellow; -- used humorously or contemptuously; as, a sly
      dog; a lazy dog. [Colloq.]
      [1913 Webster]

   4. (Astron.) One of the two constellations, Canis Major and
      Canis Minor, or the Greater Dog and the Lesser Dog. Canis
      Major contains the Dog Star (Sirius).
      [1913 Webster]

   5. An iron for holding wood in a fireplace; a firedog; an
      andiron.
      [1913 Webster]

   6. (Mech.)
      (a) A grappling iron, with a claw or claws, for fastening
          into wood or other heavy articles, for the purpose of
          raising or moving them.
      (b) An iron with fangs fastening a log in a saw pit, or on
          the carriage of a sawmill.
      (c) A piece in machinery acting as a catch or clutch;
          especially, the carrier of a lathe, also, an
          adjustable stop to change motion, as in a machine
          tool.
          [1913 Webster]

   7. an ugly or crude person, especially an ugly woman. [slang]
      [PJC]

   8. a hot dog. [slang]
      [PJC]

   Note: Dog is used adjectively or in composition, commonly in
         the sense of relating to, or characteristic of, a dog.
         It is also used to denote a male; as, dog fox or g-fox,
         a male fox; dog otter or dog-otter, dog wolf, etc.; --
         also to denote a thing of cheap or mean quality; as,
         dog Latin.
         [1913 Webster]

   A dead dog, a thing of no use or value. --1 Sam. xxiv. 14.

   A dog in the manger, an ugly-natured person who prevents
      others from enjoying what would be an advantage to them
      but is none to him.

   Dog ape (Zool.), a male ape.

   Dog cabbage, or Dog's cabbage (Bot.), a succulent herb,
      native to the Mediterranean region (Thelygonum
      Cynocrambe).

   Dog cheap, very cheap. See under Cheap.

   Dog ear (Arch.), an acroterium. [Colloq.]

   Dog flea (Zool.), a species of flea (Pulex canis) which
      infests dogs and cats, and is often troublesome to man. In
      America it is the common flea. See Flea, and
      Aphaniptera.

   Dog grass (Bot.), a grass (Triticum caninum) of the same
      genus as wheat.

   Dog Latin, barbarous Latin; as, the dog Latin of pharmacy.


   Dog lichen (Bot.), a kind of lichen (Peltigera canina)
      growing on earth, rocks, and tree trunks, -- a lobed
      expansion, dingy green above and whitish with fuscous
      veins beneath.

   Dog louse (Zool.), a louse that infests the dog, esp.
      H[ae]matopinus piliferus; another species is
      Trichodectes latus.

   Dog power, a machine operated by the weight of a dog
      traveling in a drum, or on an endless track, as for
      churning.

   Dog salmon (Zool.), a salmon of northwest America and
      northern Asia; -- the gorbuscha; -- called also holia,
      and hone.

   Dog shark. (Zool.) See Dogfish.

   Dog's meat, meat fit only for dogs; refuse; offal.

   Dog Star. See in the Vocabulary.

   Dog wheat (Bot.), Dog grass.

   Dog whelk (Zool.), any species of univalve shells of the
      family Nassid[ae], esp. the Nassa reticulata of
      England.

   To give to the dogs, or To throw to the dogs, to throw
      away as useless. "Throw physic to the dogs; I'll none of
      it." --Shak.

   To go to the dogs, to go to ruin; to be ruined.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Dog \Dog\, v. t. [imp. & p. p. Dogged; p. pr. & vb. n.
   Dogging.]
   To hunt or track like a hound; to follow insidiously or
   indefatigably; to chase with a dog or dogs; to worry, as if
   by dogs; to hound with importunity.
   [1913 Webster]

         I have been pursued, dogged, and waylaid. -- Pope.
   [1913 Webster]

         Your sins will dog you, pursue you.      --Burroughs.
   [1913 Webster]

         Eager ill-bred petitioners, who do not so properly
         supplicate as hunt the person whom they address to,
         dogging him from place to place, till they even extort
         an answer to their rude requests.        -- South.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dog
    n 1: a member of the genus Canis (probably descended from the
         common wolf) that has been domesticated by man since
         prehistoric times; occurs in many breeds; "the dog barked
         all night" [syn: dog, domestic dog, Canis familiaris]
    2: a dull unattractive unpleasant girl or woman; "she got a
       reputation as a frump"; "she's a real dog" [syn: frump,
       dog]
    3: informal term for a man; "you lucky dog"
    4: someone who is morally reprehensible; "you dirty dog" [syn:
       cad, bounder, blackguard, dog, hound, heel]
    5: a smooth-textured sausage of minced beef or pork usually
       smoked; often served on a bread roll [syn: frank,
       frankfurter, hotdog, hot dog, dog, wiener,
       wienerwurst, weenie]
    6: a hinged catch that fits into a notch of a ratchet to move a
       wheel forward or prevent it from moving backward [syn:
       pawl, detent, click, dog]
    7: metal supports for logs in a fireplace; "the andirons were
       too hot to touch" [syn: andiron, firedog, dog, dog-
       iron]
    v 1: go after with the intent to catch; "The policeman chased
         the mugger down the alley"; "the dog chased the rabbit"
         [syn: chase, chase after, trail, tail, tag, give
         chase, dog, go after, track]

The Free On-line Dictionary of Computing (19 January 2023):

dog

    An enhanced version of the Unix cat command that,
   in addition to outputting the contents of files, can output
   the data obtained by fetching URLs.  It also offers various
   output options such as line numbering.

   Unix manual page:
   (http://www.penguin-soft.com/penguin/man/1/dog.html).

   (2009-06-12)


The Devil's Dictionary (1881-1906):

DOG, n.  A kind of additional or subsidiary Deity designed to catch
the overflow and surplus of the world's worship.  This Divine Being in
some of his smaller and silkier incarnations takes, in the affection
of Woman, the place to which there is no human male aspirant.  The Dog
is a survival -- an anachronism.  He toils not, neither does he spin,
yet Solomon in all his glory never lay upon a door-mat all day long,
sun-soaked and fly-fed and fat, while his master worked for the means
wherewith to purchase the idle wag of the Solomonic tail, seasoned
with a look of tolerant recognition.