i think emotional cheating is making an emotional attachment to others while you are in a relationship. even without a physical affection to the other person, having emotionally attached to someone else is can be called cheating.
Being someone who was emotionally cheated on, I agree with this definition. My husband at the time was "in love" with this other woman our entire marriage. He told me this when he told me he was divorcing me. He and this woman would call each other on their birthdays, call each other at work, etc etc. He would bring our children over to her house with the excuse that they were getting the kids together to play, but he would stay at her house & chat with her. This occurred throughout our marriage. She even called our home a few times in the middle of the night with some problem and would ask to speak to my husband.
Meanwhile, my birthdays were forgotten and he treated me like poop calling me every name in the book.
Eventually, it got to the point where he would go to her home after work instead of coming home to me.
He claims there was nothing physical between them. I have no proof there was - before we divorced, anyway.
If that's not emotional cheating, I don't what is. I do consider that to be cheating, physical or not.