The specific quality of the blur in out-of-focus areas of the picture; "the way the lens renders out-of-focus points of light." Small highlights, especially, in the blurry areas of a photo can be rendered dramatically differently by different lenses (or "faux bokeh" photoshopping techniques).

Some examples of different types of bokeh are at en.wikipedia.org/wiki/Bokeh

A trick in photography where one part of the photo is in focus and the rest isn't, so attention is drawn to the subject. That out-of-focus area is called bokeh.

A fucking crazy woman in Japan who eats little kids. The said crazy woman will often remove the head of her children prior to eating them with a wooden spork.