Moving your vehicle just a bit forward when stopped at a red light, like as if the light had turned green. The purpose of triggerfooting to see if the stupid people in the car next to you will put their foot on the gas before they look at the light. Ideally, the person who has been triggerfooted will start to go, and then immediately slam their foot on the brakes.
"I'm going to triggerfoot that foo in the red porsche. Watch this".