493bbc30__Touch_Gesture_Reference_Guide__Platform_Description
[Platform] iPhone OS [Platform Gesture] Pinch Close [Core Gesture] Pinch [Platform Description] 
A two-finger user gesture used to zoom out. To pinch close, users place the thumb and a finger (or two fingers) a little distance apart on the screen and move them toward each other without lifting them from the screen.
LukeW | Touch Gesture Reference Guide
Platform Description