The International Infidelity Law Consortium considers the following activities infidel aka cheating. Specific implementation may vary amoung countries
- Sexual fantasy with someone outside marriage
- Talking with an attractive stranger
- Flirting
- Exchanging contact details
- Meeting up without accompanying spouse(s)
- Playful touching
- Kissing
- Erotic massage
- One night stand
- Regular sexual intercourse
- Established affair with long term commitment
Source: https://en.wikipedia.org/wiki/Infidelity#Research_issues