The trunk of some people's cars may contain items as disparate as old clothes, rotting food, and possibly a missing relative. Disparate things are very different from each other.
Near synonyms are unequal and dissimilar. The adjective disparate is from Latin disparātus, from disparāre "to separate, divide," from the prefix dis- "apart" plus parāre "to prepare." Disparate in the sense of "very different" probably developed by association with the Latin adjective dispar "unequal, different."