Definition of shortstacker
A shortstacker is not a shortstack in tournaments. If you always buy in for 20 big blinds in cash games, you are probably a shortstacker, that is, a player who has perfected his shortstack strategy. This shortstacker player has decided to be a shortstack, he knows exactly what he is doing. When you have 20 or 10 or 5 big blinds in tournaments, it's not by choice; the hands haven't always gone our way. In these moments, we will feel the urgency to make a "move", that is to say to make an aggressive EV+ play to hopefully double or triple our stack. Cash game shortstacking and tournament shortstacking do not have the same motives.