Not to highjack - what is trigger slap?
Three are three definitions I can think of off hand, the one that seems to apply here is an interaction between the slide, the disconnector, and the trigger return mechanism that snaps the trigger forward when the slide returns to battery. It can sting your finger and add up after shooting for a while.
Some folks call trigger slap what I think of as trigger pinch. Trigger pinch is when the fleshy part of your finger get pinched between the bottom of the trigger and the trigger guard when the trigger resets.
Finally, some shooters slap the trigger to increase speed instead of riding the reset. Some very good shooters, such as Rob Leatham, are trigger slappers, but it's not for everyone.
