Hard to Define Humility

Humility is one of those words that is hard to define.  Like glory.  Or beauty.  Or love.  It's just easier to spot it, than it is to define it.  Yesterday, however, I heard a great definition of humility that sums it up pretty well.  Not suprisingly, C.S. Lewis, a brilliant, yet child-like man of God, penned the quote. 

Humility is not thinking less of yourself, it's thinking of yourself less.

Something to ponder this week.  Any other good definitions or quotes on humility?