Final answer:
Realignment refers to the period when the dominance of one of the two major political parties is replaced by the other, signifying a shift in the political balance of power.
Step-by-step explanation:
The term that refers to a transition period when a party system dominated by one of the two major parties is replaced by another system dominated by the other party is known as realignment. Realignment occurs when there are shifts in party allegiance in response to changes in party position, demographic changes, or critical events, leading to a new balance of political power. Throughout U.S. history, there have been several periods of realignment, where control of the presidency shifts from one party to another, or there are significant changes in a party's makeup, signaling an adjustment in the political landscape.