double standard

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A set of principles permitting greater opportunity or liberty to one than to another, especially the granting of greater sexual freedom to men than to women.

Century Dictionary and Cyclopedia

1. That may be registered in two classes: applied to cattle. Thus the double-standard polled Durhams may be registered as shorthorns or as polled Durhams.

Wiktionary

1. n. The situation of two or more groups, one of whom is tacitly excused from following a standard generally regarded as applying to all groups.
2. n. The sexual mores applied to men (who are permitted to wander) vs. those of women, (who are expected to be chastely faithful).

GNU Webster's 1913

1. adj. a double standard of monetary values; i. e., a gold standard and a silver standard, both of which are made legal tender.
2. n. a standard or set of principles governing conduct, which is applied more stringently or differently to one group of people than to another; -- used especially of standards of sexual behavior that condemn behavior on the part of women that is condoned or not condemned when exhibited by men.

WordNet 3.0

1. n. an ethical or moral code that applies more strictly to one group than to another