A spinner is a winning streak, the kind of run that makes other players at the table start paying attention. If someone calls you or your streak a spinner, it is praise: they are saying you are on a roll.
The exact origin is unknown. The usual explanation points to the two games built around spinning: to play roulette the croupier must spin the wheel, and every slot round starts with a spin of the reels. Players who kept winning on either were half-jokingly suspected of controlling the wheel or the reels, and the nickname for their streak followed.
Winning streaks from the operator’s side
A game’s RTP and volatility are fixed by its maths model, and each round is independent, so streaks are expected statistical noise rather than a pattern; believing a streak must continue or end is the gambler’s fallacy. Operators still watch them: visible wins create buzz in live lobbies and win feeds, while unusually consistent runs are worth a quick review by the risk team.