It's really a pretty specific idea initially coined in Clayton Christensen's book "The Innovator's Dilemma."
From the book, via Wikipedia:
"Generally, disruptive innovations were technologically straightforward, consisting of off-the-shelf components put together in a product architecture that was often simpler than prior approaches. They offered less of what customers in established markets wanted and so could rarely be initially employed there. They offered a different package of attributes valued only in emerging markets remote from, and unimportant to, the mainstream."
So the canonical example would be PCs disrupting the market for mainframes or minicomputers. Or as described in the book, less powerful hydraulic excavators disrupting steam-powered excavators. It's a good book, anyone who is interested in the business of technology should read it.
The contradiction is that disruptive products are usually much worse products than the ones they eventually replace. No one who owned a VAX or a mainframe looked at the first IBM PCs and thought that the PC was a "better" product. But the PC started cheaper, stayed cheaper and got better fast enough to displace minicomputers while at the same time opening up an entirely new market for computers that didn't exist before.
So much of this hinges on how you define what "disruptive" means. There's an argument to be made that the iPhone started the trend of phones & tablets disrupting the entire desktop PC industry, starting as "worse" products that eventually replaced the "better" product. I personally don't think you could really say the iPhone "disrupted" Blackberry per se - their relationship is more like early Compaq to IBM where Compaq/Apple put out a much better product that broke down barriers holding the original product back (e.g. Compaq decoupling bus speed from processor speed allowing them to ship a faster computer with an ISA-compatible bus for expansion cards).