To make or become less strong or powerful. The long illness had weakened him considerably.
To reduce the intensity or effectiveness of something. The new evidence weakened the prosecution's case.
To diminish the physical strength or energy of someone or something. The harsh weather conditions weakened the structure of the bridge.
To cause a decrease in the value or quality of something. The economic crisis weakened the currency significantly.
To become less resolute or determined; to give way. Her resolve weakened and she finally agreed to the proposal.