From Longman Dictionary of Contemporary Englishlike funlike funAmerican English spoken old-fashionedWRONG/INCORRECT used to say that something is not true or will not happen ‘I’m going to Barbara’s house.’ ‘Like fun you are! Come and finish your chores first.’ → fun
Examples from the Corpuslike fun• "I'm going to Barbara's house." "Like fun you are! Come and finish your chores first."