Misuse is using something incorrectly or in a harmful way. I warned you that repeated misuse of your cellphone would break it — I can't believe you were texting in the shower!
You can use this word as a noun or a verb, with just a slight change in pronunciation. As a noun, misuse rhymes moose. But when you misuse the money your parents gave you for groceries, spending it all on candy and comic books, misuse rhymes with confuse. A less-common meaning of the verb is "treat someone badly."