"To weaken the dollar" means reducing the value of the currency compared to other currencies. It can make imported goods more expensive but boost exports and make travel abroad cheaper. Full definition
We are confident in saying that a miss here would weaken the Dollar tremendously tomorrow. (futuresmag.com)
This has rekindles fears of a possible trade war which has further weakened the dollar in the international market. (policybazaar.com)
A central problem is defining currency manipulation in a way that excludes the United States — in particular, the Federal Reserve's post-recession stimulus campaign, which had the effect of weakening the dollar much in the same way that other countries do to their currency. (nytimes.com)