Thief who specializes in persuading other thieves to surrender their valuable items.
From the website of Mark Brandon "Chopper" Read:

"My apprenticeship in crime began in the 1970s. This had me robbing massage parlours and taking on contracts to maim and kill rivals. Once I had obtained a doctorate as a "standover man", robbing drug dealers and other criminals, who funnily enough couldn't report me to the police, became childs play. I once told a friend "why rob a straight guy of $20 when you can rob a drug dealer of $10,000 and he can't go running to the police?" After all both involved some work on my behalf, but the man in the street was less likely to give up his $20 as he had to work hard for it. For the drug-dealers it came easy, so why would they put up a fight. Although some of my victims chose to chew razor blades (at their own request of course), before they would hand over cash? And I am the psychopath!
by Yammer February 22, 2004
a large man, usually gang-related, who threatens people with physical violence in order to have certain wishes carried out.
by VAKI5 November 2, 2003
Aussie slang for an extortionist who uses physical violence (or threats thereof) to extract payment on behalf of another party.
You might pay a standover man to get some money owed to you instead of going via the police. Perhaps you might order a few broken ribs or a kneecapping as an object lesson to go along with the payment.
by dbb618 April 26, 2007