In radio and television broadcasting a rimshot is a station that attempts to reach a larger media market from a distant suburban, exurban, or even rural location.
Many rimshot operators attempt to serve the larger market with a signal that has deficiencies in the intended listening area, especially on the far side from where it is transmitted.
Many (if not most) rimshot stations are "move-ins", having moved to about halfway between their city of license (which they are legally required to cover and serve) and the metro area which they actually care about.
These are primarily Mexican AM stations operating at very high power on clear channels to reach the American Southwest and beyond via skywave at night.
Hence, English-language duopolies in major Canadian markets have involved stations licensed to rimshot major cities or serve different portions of a larger metropolitan area (such as Victoria and Chilliwack for Vancouver, Hamilton and Barrie for Toronto, Pembroke for Ottawa and Sherbrooke for Montreal).