class action lawsuit; class action
Legal term referring to a lawsuit in which a group of people with the same or similar injuries caused by the same product or action sue the defendant as a group.
Class action lawsuits are often used in consumer litigation involving many victims.
集団訴訟 is a broader term for any group litigation, while 複雑訴訟形態 specifically refers to the procedural form of a class action under Japanese law.
Compound of 複雑 (complex) + 訴訟 (lawsuit) + 形態 (form). The term is a direct translation of the legal concept 'class action'.