reiten = to go (horseback) riding / to go riding
In English, I would not use it without "go", but reiten is used alone.
It's not as clearcut as that. As I said above, 'go riding' I would translate, in most contexts, as 'reiten gehen' or 'ausreiten'. There are loads of phrases where I would use 'ride' without 'go', e.g.
How often do you ride?
Do you ride dressage?
How long should you wait before you ride after feeding?
I've always ridden thoroughbreds
How would translate the simple sentence:
"My family and I went horseback riding on the weekend."?
Meine Familie und ich sind am Wochenende ausgeritten (if that's what you did)/ sind am Wochenende reiten gegangen/ waren am Wochenende reiten (but this last is a bit colloquial IMO)
In any case, as also mentioned above, 'went' does not go with 'ist/hat geritten', so if that's the entry, it's wrong anyway. German often uses Perfekt when English uses simple past, but I don't think that makes it a correct match for a Flexionstabelle.