The term 'make a jumper, say' can be solved by the four letter word 'KNIT'. Knitting is an activity that involves using two needles to interlock loops of yarn or thread to create a fabric. It is a popular craft that has been around for centuries and is used to make clothing, blankets, and other items. To make a jumper, one would use knitting needles and yarn to create a garment that covers the torso and arms.