to place the thumb and a finger of one hand on the screen of an electronic device such as a mobile phone or small computer and move them together or apart, to make the image on the screen appear smaller or larger
لمس دو انگشتی, فشردن صفحه با دو انگشت, بزرگنمایی با دو انگشت, کوچکنمایی با دو انگشت
You can pinch and zoom in.
see also flick, spread, tap