How do you define infidelity (cheating)?
Having an affair?
Hooking up after a drunk night?
Paid sex with an escort/prostitute
Happy ending massage?
French kissing someone?
Staying active on a dating site?
Flirting?
Sexting?
Infidelity is defined by the couple themselves. So any act or thought that one cannot share with or wilfully accept by the partner is very likely an indiscretion.