The word "elude" functions as a verb and it means to escape. The word's real meaning, however, can vary very significantly from one sentence to another. A book, lecture or speech described as "elusive" means that it is unclear, convoluted or difficult to understand. In this case, the term functions as a negative adjective and can serve as a form of criticism. On the other hand, someone who eludes the attention of others can be seen as clever. The word "elude" is generally a more formal way of saying "escape," and it is the best term to use in essays or in professional speech.