A mixed metaphor combines two or more metaphors that do not fit together logically, often in the same sentence or phrase. The result can sound striking, comic, or awkward, depending on the writer's intention and how well the images are controlled.
Poets and speakers usually avoid mixed metaphors unless they want to create surprise, irony, or humor.
Example
We were sailing through a storm of paperwork,
trying to keep our feet on the rails.
[n] a combination of two or more metaphors that together produce a ridiculous effect