The dollar gap refers to the shortfall of U.S. dollars needed by European countries to finance their post-World War II economic recovery. As Western European nations emerged from the devastation of the war, they faced a significant lack of available currency, which hindered their ability to import goods and stimulate economic growth. This shortage was critical because it limited their access to American products and investment, stalling their recovery and overall economic stability during the late 1940s and early 1950s.