at your best/worst/most effective etcXXused to say that, at a particular time, someone or something is as good, bad etc as they can be 处于最佳/最差/最有效等的状态 The garden is at its best in June. 这个花园在六月份的时候景色最美。
This was Federer at his most powerful. 这是费德勒的巅峰时期。
→ at your best/worst/most effective etc at at(1)