Dictionary
un'ion bust"er
1. any of a group of persons hired by a company to disperse picketers, end a strike or job action, etc., esp. by violence or intimidation.
2. any person or group that tries to destroy or weaken a union, as through prosecution or intimidation:
The district attorney has a reputation as a union buster. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.