Cut from a single "brick" of aluminum, purportedly, the new MacBook Pro is a sculpture: it exists in the marble, waiting to be cut free by the chisel. Or the laser. You know.
From this shot, which appears to have a seam between side and top, it rather appears the whole brick thing refers to laser-cutting the MacBook Pro's new, thicker keyboard panel to get it to match in the style used on the MacBook and desktop keyboards (and by Sony). If this speculation is true, and I dearly hope it isn't, "brick" is the most absurd lot of hype the universe has seen since the first crusade. Or the Amiga CDTV. You know.
Nonetheless, it looks nice. The crap photo is convincingly mundane, no?
Update: Gizmodo exhaustively explores this very line of thought.