Dull, dreary, dingy, depressing: These adjectives capture the sense of drab, whether the word is used to describe a muted color, a miserable mood, or an oppressively boring existence.
Have you ever heard of the color olive drab? It's the color the military clothes its soldiers in and is the original meaning of the word drab. A little over 100 years ago, people began using drab in the metaphorical sense to mean "dull" and "lacking brightness." If a website or an advertisement is drab, the page is boring and unattractive. If it is cold and rainy for a week, you'll get awfully tired of those drab days, and a great teacher can make even the drabbest book come to life.