Bipartisan is defined as "relating to or involving members of two political parties."
In a two-party system, like in the United States, bipartisan typically refers to any bill, act, resolution or any other action of a political body in which both of the major political parties, Republicans and Democrats, are in agreement. Often, compromises are called bipartisan if they reconcile the desires of both parties from an original version of legislation or other proposal, and Often, bipartisanship is referred to "meeting in the middle." This interpretation brings bipartisanship closer to the more applied notion of postpartisan decision-making, a solution-focused approach that creates a governance model with third-party arbiters used to detect bias.
Failure to attain bipartisan support in such a system can easily lead to legislative gridlock, often angering each other, their constituencies and the general public. This is often caused by an increased polarization of the two major parties in power.