My manager keeps pretending to punch me in the groin when I walk past. This happens at least once on every shift. I have asked him to stop doing it more than once, as it makes me jump back and I suffer from a back injury, so it can be quite painful. He laughs about it when he does it, and I am sure he does it in jest, but he refuses to stop doing it. He simply laughs and says he would never actually hit me there, but it’s automatic to jump back out the way.

My friend who is a store manager in another store informs me that because of where he aims, it can be deemed as sexual harassment. Is this the case and what is the way forward?

No idea. Document your complaint - use company email. Send at least two. One personal, and one CC'd to HR.
Then take the documentation to a lawyer, and consult.

I'll try to phrase this as careful as possible, but English isn't my mother tongue....

Accusation of sexual harassment shouldn't be taken lightly, as it is a major crime. It shows a kind of desperation when you try to go down this route. I don't want to euphemise your suffering, but point out that this route is a very dangerous one...

Leave legal terms to lawyers - they know exactly what term should be used and if they misuse it it falls back on them - not you. Bad sexual harassment is a pretty legal term with a lot of nasty ifs.

What's definitely happening here is that your manager plays tricks on you. And your manager doesn't seem to respect your wish to stop this behaviour.

Keep it neutral like this. Talk to HR.

Then do exactly what @magicMirror said...

Just... Tone it down and leave legal terms to a lawyer.

Yeah, i agree with @IntrusionCM. It doesn't have to be sexual harassment to be something they really need to stop doing. When a manager is making you uncomfortable at work for laughs they aren't just not doing their job correctly, they are actively hindering you doing your job which means they are wasting company money at everyone's expense.

Thank you...