He always talked big, but never amounted to anything.·他总是夸口，但毫无成就。

talk big: speak boastingly; make exaggerated statements or excessive claims in order to impress people 说大话；吹大牛；言过其实；以期引人注目。
　　再如:
　　We dislike those who talk big and do nothing.
　　我们不喜欢那些专讲大话而不做事的人。