An adherent to a party or faction.

A fervent, sometimes militant, supporter or proponent of a party, cause, faction, person, or idea.

A member of a band of detached light, irregular troops acting behind occupying enemy lines in the ways of harassment or sabotage; a guerrilla fighter.

Serving as commander or member of a body of detached light troops.

“partisan officer, partisan corps”

Adherent to a party or faction; especially, having the character of blind, passionate, or unreasonable adherence to a party.

“They were blinded by partisan zeal.”

Devoted to or biased in support of a party, group, or cause.

“partisan politics”