up in arms

adjective3

1. •
   Armed for battle; prepared for or engaged in warfare.

   • March on, march on, since we are vp in Armes, If not to fight with forraine Enemies, Yet to beat downe these Rebels here at home. — 1593
2. •
   (figurative) Angry; incensed; preparing for a fight.

   • The union members are up in arms over threats of pay cuts.
3. •
   (figurative) Vigourously protesting against something.

   • Is file-sharing, which has the recording industry so up in arms, the “dark side” of open-source attitudes? — 2003