I've been in a very emotional, highly charged but not physically intimate relationship at the same time as being in a committed partnership with the lady who is now my wife. It was definitely emotional unfaithfulness and I spent a lot of time and effort in turmoil over it.
In my defence, I had fallen for the first lady before I met my wife, but had thought that I could manage the emotions, as she was married to someone else (that marriage only lasted a year, so there was lots wrong with their relationship too)
I stopped seeing the first lady when I realised how dangerous the situation was and how hurt my partner would be. I definitely made the right choice, but it doesn't stop me thinking "what if?" and occasionally dreaming about her.
I'd call that unfaithfulness, even though we NEVER had sex (came pretty close a couple of times).
Who was it who said that "the indiscretions you most regret are the ones that you don't commit"?