This is more of a fun word game than a writing exercise, but sometimes it is good to wake up your brain and just be silly with words.
Grab a dictionary and find a word that you don't know the meaning of. When you find one - do not look at the meaning! Jot down the word on a piece of paper and make up your own meaning for it. Then search for another word. Keep going and let yourself get more and more outrageous. Maybe when you have a list of silly words you'll be inspired to write a nonsensical poem.
(*When you are finished you may want to look up the actual meanings of the words. Did you have any of them right? Close? I hope not!)