When one is browsing content, often online or flicking channels on TV, with no intention of fapping
either then or later, but are forced to or reminded to fap upon seeing something. That thing is a fap trap.
Bro 1: "Dude I wasn't even gonna fap tonight but then I was flicking music channels and the video for Call on Me by Eric Prydz came on and I couldn't not afterwards."
Bro 2: "Yeah that video is such a fap trap"