Definition of downswing
A downswing is when you accumulate losing sessions over a short, medium or long period of time. There is no rigid definition of a downswing, but if you are a winning player who is used to having winning sessions most of the time and you have 5-6 losing sessions due to terrible beatbeats, you can say that you are in a downswing. The downswings come in as much for tournament players, sit'n'gos only games of cash games. And you will know more downswings in some variations than in others. For example, you will have more downswings in tournament than in cash games and you will have more downswings in Omaha than in Hold’em.
Winning players and downswing
A bad player who has 20 bad sessions may not necessarily be in downswing. If you are a long-term loser and do not play optimally, losing over a long period of time will not be a downswing, but the consequence of your bad decisions. In order to be a downswing, you must have proof that you are a winning player. A downswing can be short (less than downswing losing sessions), medium-long (losing 40 of the last 50 sessions) and long (downswing then spreads over a year or two). The downswings are inevitable. Even the best players in the world have downswings.