Definition of "Dog" :
noun: 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."
noun: metal supports for logs in a fireplace
noun: a hinged catch that fits into a notch of a ratchet to move a wheel forward or prevent it from moving backward
noun: a smooth-textured sausage of minced beef or pork usually smoked; often served on a bread roll
noun: someone who is morally reprehensible
"You dirty dog."
noun: informal term for a man
"You lucky dog."
noun: a dull unattractive unpleasant girl or woman
"She's a real dog."
verb: go after with the intent to catch
"The dog chased the rabbit."