庸庸碌碌 is a four-character idiom (chengyu) that describes a person who is completely ordinary, unremarkable, and lacking any ambition or achievement — the kind of mediocrity that suggests a wasted life. It's more dismissive and literary than just 'average'; you'd use it to criticize someone who has never done anything noteworthy. The reduplicated structure (AABB) intensifies the sense of blandness.