A set of methodologies which aim at incorporating optimizations for later stages of production, servicing or disposal of a product right at the design phase. X is a placeholder for the aspect that is being optimized for. Some examples of such methodologies include Design for Manufacturability (DfM - maximising the ease with which a product is manufactured), Design for Reliability (DfR – preventing failure of the product for a given amount of time), or Design for Logistics (DfL – minimising logistical costs).
DfX is also known as Design for eXcellence.