Pretty much all of my stims are invisible to the outside world; it's how I was trained growing up. And possibly like you, I only recently learned that any of those things that I did to balance internal stimulus levels (ie in the brain*) with sensory-nerve signal levels (by upping the latter) are indeed, stimming. And stimming doesn't necessarily have to be highly repetitive, it's just that most physical stimulus is one-shot, like a hand clap. It ends and you have to do it again. Imperfectly constant pressure and vocal stimming would be examples of non-repetative stims.
*and this includes, frustratingly enough, brain levels that are induced by external stimulus not under the person's control, like auditory stimulus from a room full of talking people.
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“For small creatures such as we the vastness is bearable only through love.”
―Carl Sagan