[noun] - (an act of) having sex with someone who is not your husband, wife or regular sexual partner, or (an example of) not being loyal or faithfulThe papers were full of moral judgements on marital/sexual infidelity. [U]The marriage broke up because of the wife's infidelity. [U]She could not forgive his many infidelities. [C]
INFIDELITY
Meaning of INFIDELITY in English
Cambridge English vocab. Кембриджский английский словарь. 2012