incorrigible

an incorrigible gambler/optimist/prankster不可救药的赌徒；生性难改的乐天派/恶作剧者

an incorrigible habit of playing practical jokes喜欢恶搞的积习

He is always the class clown and his teachers say he is incorrigible.他总是班里的活宝，老师们说他积习难改。