A strikebreaker is someone hired to do the work of employees who are on strike. When workers go on strike (they refuse to work until their employer agrees to better pay, safer conditions, or fairer treatment), the company might hire strikebreakers to keep the business running. These replacement workers cross the picket line, where striking workers stand outside their workplace with signs, trying to pressure the company to negotiate.

Strikebreakers are also called scabs, a harsh term that shows how striking workers feel about people who undermine their efforts. From the strikers' perspective, strikebreakers weaken their bargaining power: if the company can easily replace them, why would the employer agree to their demands? From the strikebreaker's perspective, they might simply need work and see a job opportunity.

Throughout history, the use of strikebreakers has sparked intense conflict. Companies have sometimes hired private security forces to protect strikebreakers, leading to violent clashes. In 1892, at Carnegie Steel's Homestead plant in Pennsylvania, a battle between strikers and guards protecting strikebreakers left several people dead. Conflicts like this helped shape modern labor laws about workers' rights to organize and strike.

Today, using permanent replacement workers during strikes remains legal in many situations, though it's controversial. Understanding this word means understanding one of the central tensions in labor disputes: the struggle between workers seeking better conditions and employers trying to maintain operations.