I see this term used quite a bit, what makes one market less efficient than another and how does one recognize this property?
These ideas come mostly from academia -- I'm sure you've heard of Eugene Fama, EMH, etc. http://en.wikipedia.org/wiki/Efficient-market_hypothesis For something that's probably closer to the timeframe of traders, I suggest checking this guy's work out: http://tuvalu.santafe.edu/~jdf/SFI Template/PubsEconomics.html
occam got it right, its academics. the efficient market hypothesis claims markets have some level of efficiency to it: weak, semi-strong, and strong. this refers to the transparency of information and how quickly the market reflects new information. efficient market means new information is taken in quick (think gap movements); inefficient means slow.