Mixed metaphors are usually speech mistakes by people, and are very amusing. Here are a few examples.Is there a single word for denoting mixed metaphors?
I had to go to the reverse dictionary for this one.
From what I understand, a mixed metaphor is an example of a catachresis, but not all catachreses are mixed metaphors. Wikipedia says that "Catachresis is 'misapplication of a word, especially in a mixed metaphor' according to the Penguin Dictionary of Literary Terms and Literary Theory."
Here's Merriam-Webster's definition of the word: