A strikebreaker (sometimes derogatorily called a scab, blackleg, or knobstick) is a person who works despite an ongoing strike. Strikebreakers are usually individuals who were not employed by the company prior to the trade union dispute, but rather hired after or during the strike to keep the organization running. "Strikebreakers" may also refer to workers (union members or not) who cross picket lines to work.
Aka Wikipedia 🙄

a : a contemptible person
b (1) : a worker who refuses to join a labor union (2) : a union member who refuses to strike or returns to work before a strike has ended (3) : a worker who accepts employment or replaces a union worker during a strike (4) : one who works for less than union wages or on nonunion terms / dictionary Merrian-Webster