Vivid adjectives are adjectives that create an image in your mind. Eg. You might describe the sunset as a "brilliant scattering of red and yellow hues glittering over the ocean." This hopefully helps...
A vivid adjective is an adjective which is intense. It brings a picture, sound, smell or sensation to your mind. For example, the word shiny is not very vivid, but the word glittery is more vivid.