to spend your time doing nothing and feeling sorry for yourself 闷闷不乐；自怨自艾 Extra ExamplesIt would benefit no one if we all sat moping for the next week. 如果我们都坐下一个星期，这对任何人都没有好处。 You should build on the little triumphs rather than moping about disasters. 您应该以小小的胜利为基础，而不是为灾难而烦恼。
Word Originmid 16th cent. (the early noun sense being ‘fool or simpleton’): perhaps of Scandinavian origin; compare with Swedish dialect mopa ‘to sulk’.