Be Kind, I don't know if you listen to podcasts, but The Neurodivergent Woman podcast did a really good episode on stimming recently.
They talk to a woman who is doing research on stimming from an autistic perspective.
Basically the "official" established view is that stimming is a repetitive movement behaviour that serves no purpose. (notice the neurotypical point of view!)
But autistic people tend to define stimming as any behaviour that helps you regulate yourself. It might be repetitive movement (tapping, rocking, flapping hands) or it might be listening to nature sounds, or looking at patterns and colours, or saying satisfying phrases.
The definition of stimming, from an internal, autistic perspective is the intensity of the experience, and that it helps you regulate yourself.