{v. phr.} To illegitimately and forcefully intrude into someone's traditional sales or professional arena of operation. * /Tim has a good sales territory, but he is always afraid that someone might chisel in on it./ * /Las Vegas casino owners are concerned that the Mafia might muscle in on their territory./
{v. phr.} To intrude; penetrate; force oneself into another's business or territory. * /The eastern Mafia muscled in on the western Mafia's turf and a shooting war was started./