Malapropism

Malapropism is the process of attempting to use a word, and instead using a similar-sounding word with a different meaning. See My Immortal: "Snap was taking a video tape of me and Loopin was masticating to it" (as opposed to "masturbating").

''"You keep using that word. I do not think it means what you think it means." ~The Princess Bride.''