When you have a sudden, random, inexplainable urge to buy something: for no particular reason. And you end up regretting wasting money on said thin, when you never use it.
Derek: I was in a mosque in Turkey and I just totally had to buy a Koran.
Bob: Dude, you don't even read your Bible.
Derek: I know I wasted 5 million turkish lire!! aaaahh - total impulse buy
someone who cannot resist the temptation of buying things when seen, things like coffee mugs telescopes grenade launchers jewelery porn and other adult toys
look at all this shit(a talking to b after a(s) mothers death while cleaning out her house)fuck.. she must have been one of those impulse buyers