dog 
(dôg, dŏg)
(dôg, dŏg)n.
1. A domesticated carnivorous mammal (Canis familiaris syn. Canis lupus subsp. familiaris) occurring as a wide variety of breeds, many of which are traditionally used for hunting, herding, drawing sleds, and other tasks, and are kept as pets.
2. Any of various carnivorous mammals of the family Canidae, such as the dingo.
3. A male animal of the family Canidae, especially of a fox or a domesticated breed.
4. Any of various other animals, such as the prairie dog.
5. Informal
a. A person: You won, you lucky dog.
b. A person regarded as contemptible: You stole my watch, you dog.
6. Slang
a. A person regarded as unattractive or uninteresting.
b. Something of inferior or low quality: "The President had read the speech to some of his friends and they told him it was a dog" (John P. Roche).
c. An investment that produces a low return or a loss.
7. dogs Slang The feet.
8. See andiron.
9. Slang A hot dog; a wiener.
10. Any of various hooked or U-shaped metallic devices used for gripping or holding heavy objects.
11. Astronomy A sundog.
adv.
Totally; completely. Often used in combination: dog-tired.
tr.v. dogged, dog·ging, dogs
Idioms: 1. To track or trail persistently: "A stranger then is still dogging us" (Arthur Conan Doyle).
2. To hold or fasten with a mechanical device: "Watertight doors and hatches were dropped into place and dogged down to give the ship full watertight integrity" (Tom Clancy).
3.
a. To be persistently or inescapably associated with: Questions about his youthful indiscretions dogged him throughout his career.
b. To be recurrently or persistently in the mind; haunt: Despair dogged him in his final years.
dog it Slang
To fail to expend the effort needed to do or accomplish something.
go to the dogs
To go to ruin; degenerate.
put on the dog Informal
To make an ostentatious display of elegance, wealth, or culture.
[Middle English dogge, cur, ordinary dog (often as opposed to a hunting hound or other valuable dog), from Old English docga, dog, perhaps originally a diminutive or a hypocorism meaning "Darky, Dusky," from dox, dark, dusky (for the formation, compare Old English frox, frog, and frogga, frog, perhaps originally a diminutive).]