Question

What is a synonym it is when u like to describe something like look at the BIG dog.

Answer 1

No. an adjective is used to describe something, just like what u said: “big” dog. a synonym is a word that has exactly or nearly the same meaning of another word. for example: pretty & beautiful, tiny & small. hope this helped :)

Answer 2

A synonym is something that has a similar meaning and replaces a word.
For example: the word “Big”
You could say: large, gigantic, humongous, etc.
What you are describing is an adjective, somethings that describes a noun.

Hope this helps!!