A proportional representation method is biproportional if it's close to proportional in more than one way. For instance, a biproportional party list method might give each party close to its national support in parliament, while retaining approximate within each district as well.

Wikipedia has an article on:

These methods work by accepting some error in both types of proportionality in exchange for reasonably good results along both. A biproportional party list method of the above type might give parties with fewer votes more representatives in a few districts to ensure reasonable national proportionality, similar to the top-up seats in MMP and Scandinavian party list PR w:leveling seats.

The most commonly known biproportional apportionment method is Pukelsheim's method, which is used in Switzerland. Fair majority voting, a biproportional method with single-member constituencies, has been proposed by Michel Balinski as a solution to gerrymandering problems in the United States.