Partisan means loyal to one side and unwilling to be fair to the other. A partisan crowd, partisan politics, deeply partisan.
As a noun it means something quite different and honourable: a partisan is an irregular fighter resisting an occupying army, as in the Yugoslav and Italian partisans of the Second World War.
1adjectivepartisanLoyal to one side and unwilling to be fair to the other.
“The debate was bitterly partisan, with neither side accepting a single point from the other.”
partisan is a quality.
Italian partigiano means a defender of a party, from parte, a part.
Italian
partigiano — defender of a party
French
partisan
English, today
partisan
Built from
From French partisan, from Italian partigiano (“defender of a party”), from parte (“part”). a doublet of partigiano. Attested in English from the late 15th century in the noun sense of "party adherent", and in related adjective senses from the 16th century. The "guerrilla fighter" sense influenced by Serbo-Croatian partizan, Russian партиза́н, from the same source. The sense of "guerrilla fighter" is from c. 1690. The adjective in the military sense dates from the early 18th century.
Etymology from Wiktionary, CC BY-SA