The phrase "strong rally" means a significant and forceful increase or improvement in something, such as a stock market or sports team, usually after a period of decline or struggle. Full definition
There will be several strong rallies along the way (similar to the current rally). (netpicksetfinvestor.com)
The dollar is falling, after its longest and strongest rally since September, from a low of 89.23 to a high of 92.83, or a 4 percent rise, within three weeks. (investing.com)