someone who often fails or makes mistakes because they have very little ability or skill

He might not be such a stumblebum after all - maybe he has talent. 他也许不是这么笨的一个人——可能他也有才华的。

often failing or making mistakes because of a lack of ability or skill

Her stumblebum efforts at childcare make for hilarious viewing. 她在照顾孩子方面笨手笨脚，一系列行为让人看着都想笑。