There have been several examples recently in the London theatre of what show business calls cross-casting: men playing female roles or women men’s, the latter being much more common to offset the much larger proportion of male parts in plays -- we have had Kathryn Hunter playing King Lear and Fiona Shaw as Richard II. More fundamentally, there has been a call by Helen Alexander in Equity Journal (the magazine of the British actors’ union) for plays to be regendered to provide more female parts, by which she means the rewriting of texts to convert male parts into female ones.
This is a specific use of a term with broader application in the field of feminism and gender studies, in which it refers to a conscious or unconscious change in the sexual perception of some cultural or social activity, such as the implications of women taking on work that is traditionally considered a male preserve, or shifts in the sexual interpretation of historical events.
In common with related words like genderless, genderquake, ungendered, and transgendered it takes gender to mean “sex”, a usage designed to stress the social and cultural distinctions between the sexes rather than the biological ones. This annoys traditionalists, for whom gender can only refer to constructions in grammar, never to living things. But it is now well established, and increasingly appears in more general writing as an euphemism that avoids confusion with the use of sex to imply sexual activity.