Something is said to bipartite if it consists of two distinct parts.
In quantum information science it is often quantum systems that are shared between two parties, usually spatially separated and called Alice and Bob.
If Alice's subsystem is described by the Hilbert space HA and Bob's is described by HB, the compound bipartite system is described by the tensor product of the two spaces, HA ⊗ HB. State vectors and density operators on HA ⊗ HB are called bipartite quantum states.
- Bipartite in Wiktionary