Here's the most-accurate and concise definition of nanotechnology I have seen in a while:
Nanotechnology refers broadly to a field of applied science and technology whose unifying theme is the control of matter on the molecular level in scales smaller than one micrometer, normally 1 to 100 nanometers, and the fabrication of devices within that size range. For scale, a single virus particle is about 100 nanometers in width. More here
It comes from a post by Mat Nayie, but I am unclear as to whether he wrote it, just posted it or of the original context of the article. The definition, unfortunately, is the best part of the article. The rest paints in too-broad brushstrokes the possible energy applications of nanotechnology.
And those who doubt the feasibility of "Drexlerian" nanotechnology might be annoyed by the illustration of diamondoid gears, wheels and other imaginary doodads accompanying the article.
Oh, and the "Great Things Come In Small Packages" headline might annoy a few old-time nanopundits (myself included).
So, anyway. Nice definition. We'll leave it at that.