People have different standards of what they consider cheating, and we will probably never all agree on what exactly defines infidelity.
Huffington Post did a study at the University of Michigan that took a deeper look at exactly what behaviors people consider to be cheating.
The study asked 456 students to rate 27 behaviors on a scale of 0 to 100, 0 being not cheating, 100 being Tiger Woods.
After the most obvious, sex and oral sex, which were respectively ranked a 97.7 and 96.8, here are a few other behaviors and how they were evaluated on the cheating scale:
Kissing on the lips: 88.7
E-mailing pictures of themselves naked: 88.2
Texting erotic messages: 82.6
Sleeping in the same bed: 68.4
Holding hands: 63.2
Forming a deep emotional bond: 52.4
Sitting in lap: 52.2
Going out to dinner: 41.4
Sharing secrets: 36.5
Hugging for more than 10 seconds: 34.5
You can see the whole list here, on the seventh page.