Something that's catchy grabs your attention or sticks in your memory. A catchy TV commercial jingle is one that kids can't stop singing.
Ad executives are always seeking catchy slogans or ideas, and movie distributors work hard to put out catchy trailers for new films. Successful pop musicians have solved the puzzle of how to write a catchy song. In all of these cases, the catchy item appeals to many people and stays with them. The word dates from the 1830s, possibly from the sense of catch meaning "contract an illness that's passed from person to person."