When something is dreary it's depressing or lifeless in a rainy-day way. I finished my work, there was nothing on TV, and the rain just wouldn't stop: what a dreary day!
Dreary can refer to a feeling, a place, a time, or even a thing. It sounds a little like a combination of "drizzle" and "teary," and that's not a bad way to remember what it means. My grandmother's house was a dreary affair: run down, poorly lit, and silent but for the buzz of the florescent light in the cramped kitchen. Some might call the recession a depression: I call it dreary, either way. If the economy remains dreary like this much longer, I just might move to China.