too big for one's boots
Far less important or capable than one thinks or claims oneself to beFar less important or capable than one thinks or claims oneself to be.
» You think you're ready for that, but you're just too big for your boots.
mccarras · Tatoeba · CC BY 2.0 FRDictionary text adapted from Wiktionary (Wiktionary contributors, CC BY-SA 4.0) and Open English WordNet / Princeton WordNet (CC BY 4.0, WordNet License); shared under CC BY-SA 4.0. Example sentences and recordings are credited where they appear.