The Collaborative International Dictionary of English v.0.48:
Partisanship \Par"ti*san*ship\, n. The state of being a partisan, or adherent to a party; feelings or conduct characteristic of a partisan. [1913 Webster]WordNet (r) 3.0 (2006):
partisanship n 1: an inclination to favor one group or view or opinion over alternatives [syn: partiality, partisanship] [ant: impartiality, nonpartisanship]