Have the upper hand: To have a position of advantage, power, and/or control (over someone, something, or some situation); To have more power in a competitive situation than the other side and to be able to control things; The position of having power or being in control in a particular situation. If you have the upper hand, you have more power than anyone else and so have control.
中文释义：have the upper hand：upper是上面的；hand是手。To have the upper hand意思就是占优势，占上风。这个习惯用语源于一种古老的比赛。大家从下到上，一个接一个地轮流把手放在一根木棍上，谁的手落在最上面，谁就是比赛的赢家，或者说the winner was the player with the upper hand. 这个习语除了可以用来说人外，还可以用来指情绪。比如说，his feelings got the upper hand. 意思是他的情绪失去了控制。