What does the term short throw mean for a manual transmission?

It means that the distance the stick or gear shifter, that is the mechanisim that determines what gear your in, moves through the different positions in it's pattern, is short. Many feel that a shorter throw between gears feels sportier and ehances the feel and ability to control the mechanicals. It certainly can simply make it easier. Just consider the difference between say a truck driver changing gears using a long stick and typically having to move it several inches, even moving his body to do so for some positions, whereas a sports driver may only require wrist movements. Zoom, zoom, zoom!