Cold War Liberalism was a way of thinking and acting that was popular in the United States during the period of time when there was a lot of tension and conflict with the Soviet Union (which is what we call the Cold War period).
Basically, some people believed that the best way to protect America from the Soviet Union was to have a strong military and a robust economy. They also believed in protecting individual rights and freedoms, and they tended to be in favor of international trade and cooperation.
These people were called Cold War Liberals because they believed in a kind of liberal (which means "open-minded" or "progressive") politics that was focused on defeating communism and working cooperatively with other countries around the world. They believed that the United States had a responsibility to lead the world in this effort, and that we had to be strong and confident in our political beliefs and economic system in order to succeed.
So in a way, being a Cold War Liberal meant being very patriotic and deeply committed to protecting America from external threats while also promoting the kinds of values that make America great, like democracy, freedom, and equality.