Definition: 

MoSCoW is a prioritisation technique letters stand for:

•  Must Have
•  Should Have
•  Could Have
•  Won’t Have this time

The use of MoSCoW works particularly well on projects. It also overcomes the problems associated with simpler prioritisation approaches which are based on relative priorities

Further Reading: 

Book: The Fifth Discipline Fieldbook by Art Kleiner, Charlotte Roberts, Bryan Smith, Peter M. Senge and Richard Ross