careless;forgetful;a careless person;scatterbrain ;
例句:
Look where you're going , you lumbering great oaf!
看着点道儿, 你这个马大哈!
I'm a bit of a klutz and that can be pretty embarrassing.
我这个人有点马大哈,有时候会出一些很尴尬的事.
Don't be careless of your own safety!
对个人安全可别马大哈!