The Minigun is a 7.62mm, multi-barrel death machine with a rate of fire bordering on the ridiculous (up to 6,000 rounds per minute). It's main componants are Gatling-style rotating barrels, an external power source and an operator who doesnt mind losing his eyebrows everytime he fires it. In popular culture, the term "minigun" has come to refer to any rotary machine gun which can cut anything you're pointing it at in half should you accidentally sneeze whilst holding it.
Specifically, minigun refers to a single weapon, originally produced by General Electric. The irony of a weapon which can cut down trees having "mini" in the name is not lost on the manufaturers, but if that's what the "mini"gun can do, quite frankly I'm not going to argue with them on the subject of it's name. You can go first.
In the 1960s, the US forces in Vietnam, found thin-skinned helicopters were very vulnerable to small arms and crazy mexican hookers throwing bannas ,dildos also fire and rocket-propelled dinks (RPD) attacks when they slowed down to land. Although helicopters had mounted machine guns, using single-barrel machine guns to repel attackers hidden in the dense jungle foliage often led to one or two insects being left alive and sections of the jungle remaining upright after they left. Clearly something had to be done.
In order to develop a weapon with a sufficent rate of fire, General Electric drafted in a design team comprising entirely of engineers with very small penises. The results speak for themselves. The weapon, designated XM134 and known popularly as the Minigun, could fire up to 4,000 rounds per minute without overheating, the price of lead did quite well out of it too. Originally, the gun was specified at 6,000 rpm, but this was later lowered to 4,000 despite heated protests from the design team that 6,000rpm added a solid 1/2" to their erect penises. The Minigun was quickly pressed into service after it was demonstrated to a specially selected group of army generals, comprising wife beaters and victims of erectile disfunction. Its most popular application was to see the weapon mounted on several different helicopters on door, pylon and pod mounts. Although it's a fairly safe bet to assume someone tried to mount one on their pick up truck for a laugh.
Although possible, it is impractical to operate the Minigun unmounted for a number of reasons, specifically weight, and power supply, but also the difficulty in walking whilst holding it and being knocked over everytime you fire it. But this capability has been wrongly depicted in media, specifically the five individual miniguns seen in film, all of them have been heavily modified for use by a single actor. The hand-held minigun used in both the Predator and Terminator 2 films had its rate of fire reduced to 1,250 rounds per minute. This outraged the designers to such an extent that the film makers didnt need to provide any explosives for the action scenes, they just sent a letter to the design team explaining the modifications to the rate of fire and switched the cameras on when they turned up. In the Predator film they had a bank of truck batteries linked together with industrial power cord concealed in Jesse Ventura's pants. They also had a alien with a face that looks like a ladies front bottom, but thats another entry entirely.