Wabi-sabi represents a comprehensive Japanese world view or aesthetic centered on the acceptance of transience and imperfection. The aesthetic is sometimes described as one of beauty that is "imperfect, impermanent, and incomplete".  It is a concept derived from Buddhist teaching of three marks of existence, specifically impermanence, the other two being suffering and emptiness or absence of self nature.

Characteristics of the wabi-sabi aesthetic include asymmetry, asperity (roughness or irregularity), simplicity, economy, austerity, modesty, intimacy and appreciation of the ingenuous integrity of natural objects and processes.  

 Reference:    http://en.wikipedia.org/wiki/Wabi-sai