To respond to your 'chicken friend's' question I first looked up 'adultery' in wiki. It is defined as having sexual relations outside of marriage.
Your friend may be alluding to 'infidelity' which wiki defines as 'cheating'; ''any violation of the mutually agreed-upon rules or boundaries of a relationship'. What constitutes an act of infidelity varies between and within cultures, it does not depend on the presence of sexual behaviour.....Fidelity refers to the accuracy and integrity of self-representation, honesty or candor in an intimate, committed relationship. Integrity may be defined as 'the inner sense of wholeness deriving from honesty and consistent uprightness of character.' Infidelity is a breach of that integrity through the use of deception by one party to a committed and not necessarily monogamous relationship. This breach is experienced as a betrayal of an explicit or implicit agreement between the partners to not keep secret those matters now the subject of deception. Deception is defined as 'the covert manipulation of perception to alter thoughts, feeling, or beliefs.'