Define the word, "obtuse."
Now, as you're thinking about it, consider this: the more you've read, the more likely you are to know the meaning of that and other relatively bookish words. In fact, the more you read the more you know in general. To put it in even starker terms, the more you read, the smarter you are.
According to a paper published by Anne Cunningham of the University of California in Berkeley, reading is by far the best way to train your mind. More than conversation and even being read to, active reading increases children's vocabulary. Reading also enhances your knowledge of the world generally while making you less likely to be taken in by false information. Finally, reading helps preserve memory and reasoning into old age.
What makes reading so great? A lot of it has to do with vocabulary. According to studies, in general conversation people tend to draw on around four hundred common, frequently used words. But even in a simple children's book the word pool increases to upwards of six hundred. The more sophisticated the book, the more unusual, less commonly spoken words you encounter. There's simply no better way than reading to come into contact with a greater variety of language.
The effect of all of this is to almost literally feed the brain with knowledge. If the brain were a muscle, copious reading would be a serious, sweat-inducing workout.
By the way, "obtuse" means dull witted or, alternatively, insensitive. If you didn't know that, then hit the books.