Malapropism is the use of an incorrect word in place of a similar-sounding word, often with humorous results.
For example, saying "I'm going to the chiropractor" instead of "I'm going to the psychiatrist" is a malapropism.
Other terms that are sometimes used to describe this phenomenon:
* Spoonerism: This is a specific type of malapropism where the initial sounds of two words are switched. For example, saying "a slippery slope" instead of "a slippy slope".
* Metathesis: This is a broader term for any phonological process where sounds are rearranged within a word, including letter transposition.
While malapropism is the most common term for transposing letters in words when speaking, these other terms may be used depending on the specific context.