A nonsense word is a made-up word that doesn't really mean anything. It is like when you play with your toy blocks and make up a tower that doesn't look like anything you've seen before. It's just a fun way to create something new and use your imagination. Similarly, writers and poets use nonsense words to make their stories and poems more interesting and fun. Some famous examples of nonsense words are "supercalifragilisticexpialidocious" from Mary Poppins and "Jabberwocky" by Lewis Carroll. So, if you ever hear or see a word that you don't know or understand, it might just be a nonsense word that someone made up for fun!