Accy szn means: Accy szn - accumulator season - marks the premier betting period of the football calendar: the packed fixture schedules of autumn and spring when midweek games fill the week and every weekend. There is no real cause for parental concern; it is descriptive vocabulary rather than risky behaviour. It is sporting vocabulary and harmless in itself. If your teen uses it, context will usually make the intent clear. A short, curious question about where they heard it is usually all that is needed to know whether to follow up.