Definition of BUSHING. 1. : a usually removable cylindrical lining for an opening (as of a mechanical part) used to limit the size of the opening, resist abrasion, or serve as a guide.2.: an electrically insulating lining for a hole to protect a through conductor. See bushing defined for kids.ADVERTISEMENT.. : a usually removable cylindrical lining for an opening (as of a mechanical part) used to limit the size of the opening, resist abrasion, or serve as a guide. 2. : an electrically insulating lining for a hole to protect a through conductor. See bushing defined for kids.