First level answers to the question:
What is the meaning of the Word Dog?
Lack of any external context other than the question itself, the brain relies upon stored information for the concept of Dog:
Internal data formed through usage of the senses, taste, touch, hearing, sight, intuit and smell, each experience uniquely different.
Presuming each individual has some form of past or current experiences with the four-legged, hairy beast, an understanding, a consensus, a general agreement of what is "A Dog" becomes the shared conclusion.
The answer to every question, query or quandary becomes as pornography, obscenity, and over-all poor taste...we all know a dog when we see one but each visualizes unique images and ideas of exactly what is a dog.