From Longman Business Dictionary
strikebreakerstrike·break·er /ˈstraɪkˌbreɪkə-ər/ noun [countableC]HUMAN RESOURCES someone who is paid to do the work of a worker who is on strikeDuring the strike, the management successfully employed strikebreakers.
→ see also blackleg —strikebreaking noun [uncountableU]Limits on strikebreaking by employers are a top priority for unions.