偷香窃玉（偷香竊玉）　

◎ 偷香窃玉 tōuxiāng-qièyù

[indulge in secret relations with women;have illicit sexual relations with women] 指善于勾引诱拐女人或男女暗中通情

不过偷香窃玉,暗约私奔而已。——《红楼梦》