Basically these are the features that would be present in a 1911 style pistol:

• locked breech
• browning type linked tilting barrel with locking lugs that are mated to the slide locking lugs
• stirrup type single action trigger
• grip safety
• frame mounted manual safety and slide lock
• frame mounted slide release lever
• frame mounted magazine release

Of course the look is also one thing which I can not fully describe here but if your pistol meets all the above requirements, you can bet that it is a 1911 style pistol. For the most part though, it is the trigger mechanism which sets the m1911 apart from its other autoloading pistol cousins.

The Para Ordnance LDA pistols, for example, look very much like the m1911 but is not in fact a true 1911 style pistol as it has a double action, swivel type trigger.