Symbolism, Imagery, Allegory
Troglodyte. Xyloid. Obfuscate.
These are just a few of the words in the dictionary that Freak makes for Max. For Freak, reading and language are exciting and indicative of his over-the-top intelligence. For Max, they are obstacles to be avoided at all costs. So Freak creates this dictionary because he sees potential in Max—a potential that Max certainly doesn't see in himself.
Max doesn't read because he thinks he is dumb, but Freak helps him along by making it interesting and, more important, less intimidating. Even Max's teachers start to see a difference: "She finally gave up on trying to make me talk in class, and instead she waits until study hall, where she asks me the same questions alone and I tell her the answers" (13.7). Max has potential. He just needs to be reached in his own way.